Sputtering target, sintered article, conductive film fabricated by utilizing the same, organic EL device, and substrate for use therein

ABSTRACT

A sintered article is fabricated which contains one or more of indium oxide, zinc oxide, and tin oxide as a component thereof and contains any one or more types of metal out of hafnium oxide, tantalum oxide, lanthanide oxide, and bismuth oxide. A backing plate is attached to this sintered article to constitute a sputtering target. This sputtering target is used to fabricate a conductive film on a predetermined substrate by sputtering. This conductive film achieves a large work function while maintaining as much transparency as heretofore. This conductive film can be used to achieve an EL device or the like of improved hole injection efficiency.

TECHNICAL FIELD

The present invention relates to a transparent conductive film for usein an LCD (Liquid Crystal Display), an organic EL (Electroluminescence)device, and the like, and more particularly to the material thereof. Theinvention also relates to a sintered article and a sputtering targethaving the same composition as that of the material. Besides, theinvention relates to a sputtering target which is made of this sinteredarticle or the like and is intended for the formation of the transparentconductive film.

Moreover, the invention relates to the foregoing organic EL(electroluminescence) device, a substrate for use in this organic ELdevice, and a method of fabricating the same. To be more specific, theinvention relates to an organic EL device which is suitably applicableto displays, the light sources of printer heads, and the like inconsumer and industrial applications, a substrate for use in the organicEL device, and a method of fabricating the same.

The organic EL device may also be referred to as “organicelectroluminescence apparatus,” “organic electroluminescence device,”“organic EL light emitting apparatus,” “organic EL display,” etc. In thepresent invention, the substrate for use in the organic EL device mayalso be referred to as an electrode substrate since it is provided withan electrode.

Furthermore, the invention relates to an organic EL device using such anelectrode substrate.

BACKGROUND ART Conventional Display

Recently, with technological development of LCDs and organic ELdisplays, there have been provided a number of products that achievehigh display performance and high capability of energy saving. Sincecapable of small-size low-profile fabrication, these LCDs and organic ELdisplays are widely used as the displays of cellular phones, PDAs(personal Digital Assistants), personal computers, laptop computers(notebook computers), television sets, and the like in particular.

Organic EL devices, components of the organic EL displays, are lightemitting devices utilizing organic compounds, of which significantperformance improvements have been seen in recent years.

In general, the structures of these organic EL devices are broadlydivided, depending on what layer is interposed between the anode and thecathode which are made of transparent electrodes, into the followingtypes:

(1) A single-layer type which has the structure that only a luminescentlayer comprising an organic compound is arranged between the anode andthe cathode, or symbolically the structure of anode/luminescentlayer/cathode;

(2) A double-layer type which has the structure that two layers, a holetransporting layer and a luminescent layer, are formed between the anodeand the cathode, or symbolically the structure of anode/holetransporting layer/luminescent layer/cathode;

(3) A triple-layer type which has the triple-layer structure that a holetransporting layer, a luminescent layer, and an electron transportinglayer are formed between the anode and the cathode. Symbolically,anode/hole transporting layer/luminescent layer/electron transportinglayer/cathode; and

(4) A quadruple-layer type which has the quadruple-layer structure thata hole injection layer, a hole transporting layer, a luminescent layer,and an electron transporting layer are formed between the anode and thecathode. Symbolically, anode/hole injection layer/hole transportinglayer/luminescent layer/electron transporting layer/cathode.

When any of the device structures is adopted, holes injected from theanode and electrons injected from the cathode reach the luminescentlayer through the hole transporting layer or the electron injectionlayer, and these holes and electrons recombine in this luminescentlayer.

Incidentally, devices referable to as EL devices also include organic ELdevices of polymer type utilizing polymer compounds and phosphorescencetype light emitting devices utilizing phosphorescence, both of which areunder research.

Conventional Organic EL Device

The organic EL devices having the structures of sandwiching an organicluminescent layer between (two) electrodes as described above have beenput to intensive research, and heretofore subjected to development forsuch reasons as follows:

(1) Being fully solid devices and thus easy to handle and fabricate;

(2) Capable of self luminescence, thus requiring no light emittingmember;

(3) Having excellent visibility, suitable for displays; and

(4) Easy to render full-color.

Nevertheless, there has been a known problem that organic luminescentlayers, being organic materials, are typically difficult to transportelectrons and holes through and thus prone to deterioration, easilycausing a leak current due to secular changes over a long time of use.

On such a problem, various contrivances have been made heretofore.

For example, the patent document 1 to be mentioned later shows anorganic EL device in which an energy difference between the workfunction of the anode and the ionization energy of the hole transportinglayer is reduced for the sake of longer life. The patent document 1describes that in order to achieve such an object, the anode is made ofmetal oxide materials that have a work function higher than that ofindium tin oxide (ITO) and are conductive. For example, RuOx, MoO₃, andV₂O₅ are mentioned as such conductive metal oxides. Organic EL devicesusing these metal oxides are disclosed in the patent document 1.

In addition, this patent document 1 proposes anodes of double-layerstructures in which thin films made of these conductive metal oxidematerials and ITO are laminated for the sake of improved lighttransmittance (%).

The patent document 2 mentioned below discloses an organic EL device inwhich metal wires are arranged in connection with the transparentelectrodes to reduce the resistances of the transparent electrodes.

The patent document 3 mentioned below discloses an organic EL device inwhich pieces of metal having a low work function are similarly arrangedin connection with the transparent electrodes to reduce the resistancesof the transparent electrodes.

The patent document 4 mentioned below discloses an example of an ELdevice that uses an auxiliary metal film. A special insulative film isarranged on the auxiliary metal film to avoid dielectric breakdown.

The patent document 5 mentioned below discloses an organic EL devicewhich comprises an insulative thin film layer between an electrode andan organic luminescent layer in order to allow long-term use.Specifically, the organic EL device disclosed in this patent document 5adopts the configuration that an insulative thin film layer made ofaluminum nitride, tantalum nitride, or the like is arranged between theanode layer and the organic luminescent layer or between the cathodelayer and the organic luminescent layer.

The patent document 6 discloses an organic EL device in which aninorganic material layer containing NiO and at least one additive out ofIn₂O₃, ZnO, SnO₂, or B, P, C, N, and O, or an inorganic material layermade of Ni_(1-x)O (0.05≦x≦0.5) is formed between an electrode layer andthe organic luminescent layer, with the objective of providing alow-cost organic EL device that is free of m-MTDATA, tetraaryldiaminederivatives, and the like.

The patent document 7 mentioned below discloses the technique offluoridizing an ITO surface to obtain ITO having a work function of 6.2eV.

Patent document 1

-   Japanese Patent Publication No. 2824411 (Japanese Unexamined Patent    Application Publication No. Hei 9-63771)

Patent document 2

-   Japanese Unexamined Patent Application Publication No. Hei 4-82197

Patent document 3

-   Japanese Unexamined Patent Application Publication No. Hei 5-307997

Patent document 4

-   Japanese Patent Publication No. Hei 5-76155

Patent document 5

-   Japanese Unexamined Patent Application Publication No. Hei 8-288069

Patent document 6

-   Japanese Unexamined Patent Application Publication No. Hei 9-260063

Patent document 7

-   Japanese Unexamined Patent Application Publication No. 2000-277256

Patent document 8

-   Japanese Unexamined Patent Application Publication No. Hei 9-63771

DISCLOSURE OF THE INVENTION

As above, organic EL devices, polymer organic EL devices, phosphorescentdevices, and the like require that holes be injected from the anode andthese holes be further injected to the luminescent layer through thehole transporting layer. For the sake of performing this injectionsmoothly, it is obvious that an energy barrier between the anode and thehole transporting layer is desirably rendered as small as possible. Toreduce this energy barrier, the difference between the work function ofthe anode material and the ionization potential of the organic compoundused in the hole transporting layer must be made smaller.

Various organic compounds have been proposed as hole transportingsubstances. Of these, aromatic amine compounds, or triphenylaminederivatives and carbazole derivatives in particular, are known as havingexcellent functions. Then, triphenylamine, a triphenylamine derivative;has an ionization potential of 5.5 to 5.6 electron volts. Polyvinylcarbazole, a carbazole derivative, has an ionization potential of 5.8electron volts.

Meanwhile, as for the transparent conductive film, indium oxide-tinoxide (ITO: Indium Tin Oxide) is well known as one having excellenttransparency and low electric resistance. Then, ITO has a work functionof 4.9 electron volts. Consequently, the anode and the hole transportinglayer made of such typical materials have a relatively large energybarrier of 0.6 to 0.9 electron volts therebetween.

Under the circumstances, for example, the aforementioned patent document8 (Japanese Unexamined Patent Application Publication No. Hei 9-63771)has proposed that a thin film made of a metal oxide having a workfunction higher than that of ITO be used as the anode of an organicluminescent device that has an organic compound layer between its anodeand cathode.

Nevertheless, the anode made of this thin film of a metal oxide istypically low in transmittance. For example, terbium oxide has atransmittance of 10%. Vanadium oxide has a transmittance of 20%. Toimprove such a low transmittance, double-layer configuration has alsobeen proposed in which a ultrathin film of the foregoing metal oxide, nogreater than 300 angstroms is laminated on an ITO thin film. Even ifthis double-layer structure is adopted, however, the transmittance is onthe order of 40-60%, which obviously is a rather small value as thetransmittance of a display. As a result, the conventional thin film of ametal oxide has been insufficient in transparency.

First Object

The present invention has been achieved in view of the foregoingproblems, with the objective of providing a highly-transparentconductive film to make the anode of an organic EL device or the like,the conductive film having a work function higher than heretofore. Thisconductive film can be used to achieve an EL device and the like ofimproved hole injection efficiency. This is the first object of thepresent invention. As will be described later, the aspect of a firstgroup of invention is mainly intended to achieve this first object.

Now, the organic EL device disclosed in the foregoing patent document 1seems to be still insufficient in the hole mobility and in durabilitydespite the use of such metal oxide materials as RuOx, MoO₃, and V₂O₅.In addition, the metal oxide materials such as RuOx, MoO₃, and V₂O₅ havelight absorption coefficients of 27000 cm⁻¹ or higher, exhibiting highvalues. This means higher degrees of coloring. Anode layers made ofthese metal oxide materials thus show as extremely low lighttransmittances (%) in the visible light range as, for example,approximately 1/9 to ⅕ that of ITO. This leads to the problem that theluminous efficiency is low and the amount of light available to exterioris small for an organic EL device. The presence has also been confirmedof the problem that even with the anodes of double-layer structure inwhich the thin films made of these metal oxide materials and ITO arelaminated, the light transmittance (%) is of the order of approximately½ that of ITO, still a small value not for practical use. In the case ofconstituting an anode layer of this double-layer structure, there isalso the problem that ITO and the metal oxide thin film must be limitedto respective predetermined ranges of thicknesses, which means a largeconstraint on fabrication.

Moreover, the work function can be made greater than that of ITO,whereas the resistance becomes equal to or greater than that of ITO witha practical problem.

Now, in the organic EL device disclosed in the foregoing patent document2, aluminum nitride, tantalum nitride, or the like is used for theinsulative thin film layer. This has produced the problem that a voltageloss (voltage drop) occurs in this portion (insulative thin film layer),resulting in higher driving voltages.

Second Object

Then, the inventors of the present application have made intensivestudies on the foregoing problems, and found that the use of certaininorganic compounds in combination with the electrode layer of anorganic EL device provides excellent transparency and durability alongwith excellent luminescence intensity even when a low driving voltage(for example, DC 10V or lower) is applied.

That is, the present invention has the objective of providing an organicEL device which comprises an electrode layer containing certaininorganic compounds, thereby achieving excellent transparency anddurability, a low driving voltage, and high luminescence intensity. Thepresent invention further has the objective of providing a method offabricating an organic EL device by which such an organic EL device canbe fabricated with efficiency. This is the second object of the presentinvention. The aspect of a second group of invention to be describedlater is mainly intended to achieve this second object.

Third and Fourth Objects

Now, in the method disclosed in the foregoing patent document 7, the ITOsurface is fluoridized so that the work function improves to 6.2 eV.Nevertheless, while the work function improves, the surface of ITObecomes an insulative film. As a result, there is the problem that theimproved work function is hard to achieve an effect.

The inventors of the present application have made intensive studies onthe foregoing problem, and found that a multilayer film composed mainlyof certain metal oxide and Ag (or Ag and the like) can be used incombination with the electrode layer of an organic EL device forexcellent results. Specifically, it has been found that the foregoingconfiguration can be adopted to constitute an organic EL device whichhas excellent transparency and durability and exhibit excellentluminescence intensity even under the application of a low voltage (forexample, DC 5 V or lower).

That is, the present invention has the objective of providing: anorganic EL device which comprises an electrode layer made of acombination of a certain metal oxide layer and a thin film layercomposed mainly of Ag (or Ag and the like), thereby achieving excellenttransparency and durability and exhibiting high luminescence intensityeven under the application of a low driving voltage; an (electrode)substrate for an organic EL device with which such an organic EL devicecan be obtained with efficiency; and a method of fabricating such anorganic EL device. These are the third and fourth objects of the presentinvention. The aspects of third and fourth groups of invention to bedescribed later are the inventions mainly intended to achieve the thirdand fourth objects.

Fifth Object

Now, the organic EL devices disclosed in the foregoing patent document 2and the foregoing patent document 3 have had the problem that the metalwires for auxiliary use can cause a difference in level which easilydisconnects opposed electrodes for a display defect. There has also beenthe problem that small charges injected from the metal wiring to anorganic layer of the organic EL device, such as the hole injectionlayer, tend to cause so-called crosstalk.

The inorganic EL device disclosed in the foregoing patent document 4 hasalso had the problem that the thicknesses of the auxiliary metal filmand the insulative film cause a difference in level, easilydisconnecting opposed electrodes.

Moreover, in the case of ITO disclosed in the foregoing document 7,there has been the problem that pits and projections arise at theelectrode ends after etching, so that a leak current flowing between theanode and the cathode can lower the luminescence intensity or precludeluminescence.

The inventors of the present application have made intensive studies onthe foregoing problems, and found that a multilayer film which comprisesauxiliary wiring of certain metal acid and has a surface layer of 5.6 eVor higher in work function and 10 Ωcm or higher in specific resistanceall over can be used in combination with the electrode layer of anorganic EL device to provide excellent transparency and durability alongwith excellent luminescence intensity even under the application of alow voltage (for example, DC 5V or lower).

That is, the present invention has the objective of providing: anorganic EL device of high luminescence intensity comprising an electrodelayer made of a combination of certain metal auxiliary wiring and asurface thin film layer, thereby achieving a significantly smallelectrode resistance, excellent transparency and durability, and a lowdriving voltage without the possibility of disconnection of opposedelectrodes or crosstalk due to a leak current; a substrate for anorganic EL device with which such an organic EL device can be obtainedwith efficiency; and a fabrication method for an organic EL device. Thisis the fifth object of the present invention. The aspect of a fifthgroup of invention to be described later is mainly intended to achievethis fifth object.

To solve the foregoing problems, the present invention adopts thefollowing means.

First Group of Invention

Initially, description will be given of the aspect of a first group ofinvention. The aspect of this first group of invention will be detailedmainly in a first embodiment to be seen later.

Invention Pertaining to a Sputtering Target

To solve the foregoing problems, the present invention is a sputteringtarget containing one or more types of metal selected from indium, zinc,and tin as a component thereof, the sputtering target containing atleast one or more types of metal selected from the group consisting ofhafnium, tantalum, bismuth, or lanthanide metal as a third componentthereof.

Since such metals as hafnium and tantalum are included as constituentelements, it is possible to increase the value of the work functionwhile maintaining transparency as in practical examples to be describedlater.

The present invention is also characterized in that the third componentmetal such as hafnium is 1% to 20% by atom in composition ratio. Below1% by atom, the effect of increasing the value of the work-function issmall. Above 20% by atom, on the other hand, the conductivity mightdrop. Incidentally, the third component metal such as hafnium ispreferably 2% to 15% by atom in composition ratio. Moreover, the thirdcomponent metal such as hafnium is yet preferably 3% to 10% by atom incomposition ratio.

The present invention is also characterized in that the lanthanide metalcomprises at least one or more types of metal selected from the groupconsisting of cerium, samarium, europium, and terbium.

Invention Pertaining to a Sintered Article

A typical example of the sputtering target is a sintered article of ametal oxide or the like. Hereinafter, the invention pertaining to thissintered article will be described.

Initially, the present invention is a sintered article containing one ormore types of metal selected from indium oxide, zinc oxide, and tinoxide as a component thereof, the sintered article containing at leastone or more types of metal oxides selected from the group consisting ofhafnium oxide, tantalum oxide, bismuth oxide, or a lanthanide metaloxide as a third component thereof.

Since hafnium oxide and the like are included as the third component, itis possible to increase the value of the work function while maintainingtransparency as in practical examples to be described later.

The present invention is also characterized in that the third componentmetal oxide such as hafnium mentioned above is 1% to 20% by atom incomposition ratio with respect to the total amount of the sinteredarticle. The present invention is further characterized in that thelanthanide metal oxide comprises at least one or more types of metalselected from the group consisting of cerium oxide, samarium oxide,europium oxide, and terbium oxide.

Moreover, the present invention is a sputtering target comprising: aflatly-worked piece of the sintered article described so far; and abacking plate of metal bonded to the worked sintered article. In asputtering system equipped with this sputtering target, a thin filmhaving the same composition as that of the sintered article can befabricated by sputtering.

Invention Pertaining to a Sputtering Target that Contains an Alloy ofIndium Oxide and Zinc Oxide

Initially, the present invention is a sputtering target comprising anindium oxide alloy containing a hexagonal layered compound of indiumoxide and zinc oxide (In₂O₃(ZnO)m: where m is an integer of 2 to 20),the sputtering target containing at least one or more types of metaloxides selected from the group consisting of cerium oxide, samariumoxide, europium oxide, terbium oxide, or bismuth oxide as a thirdcomponent thereof. The third component metal oxide is 1% to 20% by atomin composition ratio with respect to the total amount of the sputteringtarget.

Without the hexagonal layered compound, the sputtering target itself maydrop in conductivity. In the present invention, the hexagonal layeredcompound is included to avoid a drop in conductivity. The conductivityis preferably 10 mΩ·cm or smaller. The reason is that at or above 10mΩ·cm, overdischarge can occur during sputtering. Moreover, thehexagonal layered compound preferably has a crystal grain diameter of 5micrometer or smaller. The reason is that greater diameters maycontribute the occurrence of so-called nodule.

The sputtering target having such configuration makes it possible toform a transparent conductive film of low resistance and high workfunction while maintaining transparency.

Moreover, the present invention is a sputtering target characterized inthat an expression In/(In+Zn) which means the content of indium oxide inthe sputtering target has a value of 0.5 to 0.97.

Here, in the foregoing expression, In is a composition ratio of indiumin the sputtering target in terms of percents by atom, and Zn is acomposition ratio of zinc in the sputtering target in terms of percentsby atom.

When the foregoing expression has a value below 0.5, the resultingtransparent conductive film can drop in conductivity. At or above 0.97,on the other hand, etching may become difficult. The foregoingexpression preferably has a value of 0.7 to 0.95. In particular, therange of 0.8 and 0.95 is even more preferable.

The present invention is also characterized in that the aforementionedsputtering target containing indium oxide and zinc oxide furthercontains tin oxide as a component thereof.

The present invention further is a sputtering target comprising anindium oxide alloy containing indium oxide and tin oxide of 0.03% to0.3% by atom in composition ratio, the sputtering target containing atleast one or more types of metal oxides selected from the groupconsisting of cerium oxide, samarium oxide, europium oxide, terbiumoxide, or bismuth oxide as a third component thereof. The thirdcomponent metal oxide is 1% to 20% by atom in composition ratio withrespect to the total amount of the sputtering target.

The reason is that in such configuration, the conductivity might drop(the resistivity rise) when tin oxide falls below 0.03% by atom. On theother hand, when tin oxide exceeds 0.3% by atom, the conductivity maybecome lower (the resistivity higher) and the etching harder.

Moreover, tin oxide is preferably 0.04% to 0.2% by atom in compositionratio. Furthermore, tin oxide is yet preferably 0.05% to 0.15% by atomin composition ratio.

The present invention also is a sputtering target comprising an indiumoxide alloy containing a hexagonal layered compound of indium oxide andzinc oxide (In₂O₃ (ZnO)m: where m is an integer of 2 to 20), thesputtering target containing at least one or more types of metal oxidesselected from the group consisting of cerium oxide, samarium oxide,europium oxide, terbium oxide, or bismuth oxide as a third componentthereof. The third component metal oxide is 1% to 20% by atom incomposition ratio with respect to the total amount of the sputteringtarget. Ratios of the respective components fall within the ranges ofIn/(In+Zn+Sn)=0.5 to 0.95, Zn/(In+Zn+Sn)=0.03 to 0.2, andSn/(In+Zn+Sn)=0.02 to 0.3 in terms of percents by atom.

Here, in the foregoing expression, In is a composition ratio of indiumin the sputtering target in terms of percents by atom, Zn is acomposition ratio of zinc in the sputtering target in terms of percentsby atom, and Sn is a composition ratio of tin in the sputtering targetin terms of percents by atom.

According to such configuration, tin oxide has a composition ratio of0.3% by atom to 0.02% by atom as in the foregoing expression. The reasonis that if tin oxide exceeds 0.3% by atom in composition ratio, theconductivity may become lower and the etching harder. On the other hand,when the composition ratio of tin oxide falls below 0.02% by atom, theaddition of tin might not produce any effect.

Naturally, the sputtering target described so far may contain metalsother than the foregoing. Note, however, that the substances and amountsof the additives must not hinder increasing the value of the workfunction, which is an object of the present invention, or cause a dropin this value. It is also required of the substances not to lower thetransparency or decrease the conductivity (increase the resistivity).

The substances that can maintain the work function at a high valuewithout lowering the transparency or decreasing the conductivity includegallium oxide, germanium oxide, and antimony oxide.

Invention Pertaining to a Transparent Conductive Film

In the present invention, the conductive film fabricated throughsputtering by using the sputtering target described above has the samecomposition as that of the sputtering target described above, and thusis large in the value of the work function, excellent in transparency,and high in conductivity (low in resistivity).

The present invention is also characterized in that this transparentconductive film has a work function of 5.6 eV or higher. At or above 5.6eV, the value of the work function is equivalent to that of a holetransporting layer that is made of triphenylamine or the like. Thisreduces the energy barrier between the electrode and the holetransporting layer. As a result, it is possible to provide an organic ELdevice and the like which allows an improvement in hole injectionefficiency.

Second Group of Invention

Next, the aspect of a second group of invention will be described. Theaspect of this second group of invention will be detailed mainly in asecond embodiment to be seen later.

Initially, a substrate for an organic EL device of the present inventionis one comprising at least an electrode layer and a base member, whereinthe electrode layer contains at least one compound selected from thefollowing group A-1 and at least one compound selected from the groupB-1.

Here, the group A-1 includes chalcogenides, oxynitrides, or nitrides ofSi, Ge, Sn, Pb, Ga, In, Zn, Cd, and Mg. The group B-1 includeschalcogenides, oxynitrides, or nitrides of lanthanides.

In another configuration, the substrate for an organic EL device of thepresent invention is one comprising at least an electrode layer and abase member, wherein the electrode layer contains at least one compoundselected from the group A-2 and at least one compound selected from thegroup B-2.

Here, the group A-2 includes chalcogenides, oxynitrides, or nitrides ofGe, Sn, Pb, Ga, In, Zn, Cd, and Mg. The group B-2 includes chalcogenidesof lanthanides.

The substrate for an organic EL device of the present invention is onecharacterized in that the electrode layer is an anode layer.

The substrate for an organic EL device of the present invention is onecharacterized in that the electrode layer is a cathode layer. Accordingto the configurations of these inventions, the combined use of acompound of the group A-1 and a compound of the group B-1 or thecombined use of a compound of the group A-2 and a compound of the groupB-2 can increase the ionization potential of the electrode layereffectively. Consequently, the substrate for an organic EL device of thepresent invention described above can be used to constitute an organicEL device which has excellent durability, a low driving voltage, andhigh luminescence intensity.

The electrode layer configured thus is also characterized by having anexcellent etching property. Moreover, since at least one group out ofthe group A-1, the group A-2, the group B-1, and the group B-2 includeschalcogenides of Si or nitrides of the same in the electrode layer, itis possible to improve the adhesion of the electrode layer to the basemember at the time of formation. In addition, the electrode layer can beformed with higher uniformity. Incidentally, when the anode layer ismade of these inorganic compounds, the ionization potential ispreferably given a value of 5.6 eV or higher in consideration of holeinjectability. When the cathode layer is made, on the other hand, theionization potential is preferably given a value below 4.0 eV inconsideration of electron injectability.

The materials mentioned in the present invention can achieve ionizationpotentials of 5.8 eV or higher, being extremely suitable for thematerial of the anode.

Moreover, the substrate for an organic EL device of the presentinvention is one characterized in that the electrode layer has aspecific resistance lower than 1 Ω·cm.

When such means is adopted, it is possible to avoid the phenomenon thatuneven luminescence occurs in the display screen due to high resistanceof the electrode layer.

Consequently, the specific resistance of the electrode layer can thus belimited in value to improve electron and hole injectability, as well asto achieve a further reduction in the driving voltage of the organic ELdevice. Incidentally, if, in contrast, the constituent material of theelectrode layer has a specific resistance above 1 Ω·cm, a double-layerstructure is preferably used which includes an electrode layer made of aconstituent material having a specific resistance lower than 1 Ω·cm.

Moreover, the substrate for an organic EL device of the presentinvention is one in which the compound of the group A-1 or A-2 is any ofchalcogenides or nitrides of Sn, In, and Zn. These compounds areparticularly low in quenching property among the compounds of the groupA-1 or A-2, and are capable of constituting an organic EL device havinghigh luminescence intensity.

Moreover, the substrate for an organic EL device of the presentinvention is one in which the compound of the group B-1 or B-2 is any ofoxides of Ce, Nd, Sm, Eu, Tb, and Ho. These compounds can be used incombination to facilitate adjusting the values of the ionizationpotential and the band gap energy in the electrode layer independently.

Moreover, the substrate for an organic EL device of the presentinvention is one in which the content of the compound of the group B-1or B-2 falls within the range of 0.5 and 30 at. % with the total amountof the electrode layer as 100 at. %. Setting the value in such a rangecan facilitate adjusting the value of the ionization potential in theelectrode layer while maintaining high transparency (lighttransmittance). Besides, the electrode layer configured thus ischaracterized by having excellent etching properties to acids and thelike.

Moreover, the substrate for an organic EL device of the presentinvention is one in which the electrode layer has a thickness within therange of 1 and 100 nm. Such configuration makes it possible to fabricatean organic EL device which has more excellent durability, a low drivingvoltage, and high luminescence intensity. In addition, when thethickness of the electrode layer is in such a range, the organic ELdevice is prevented from becoming excessively thick.

Now, the configuration of the present invention pertaining to an organicEL device will be described.

Initially, an organic EL device of the present invention is one having astructure that at least an anode layer, an organic luminescent layer,and a cathode layer are laminated in succession, wherein the anode layerand cathode layer or either one of the electrode layers contains atleast one compound selected from the following group A-1 and at leastone compound selected from the following group B-1.

Here, the group A-1 includes chalcogenides, oxynitrides, or nitrides ofSi, Ge, Sn, Pb, Ga, In, Zn, Cd, and Mg. The group B-1 includeschalcogenides, oxynitrides, or nitrides of lanthanides.

Another organic EL device of the present invention is one having astructure that at least an anode layer, an organic luminescent layer,and a cathode layer are laminated in succession, wherein the anode layerand cathode layer or either one of the electrode layers contains atleast one compound selected from the following group A-2 and at leastone inorganic compound selected from the following group B-2.

Here, the group A-2 includes chalcogenides, oxynitrides, or nitrides ofGe, Sn, Pb, Ga, In, Zn, Cd, and Mg. The group B-2 includes chalcogenidesof lanthanides.

As above, the combined use of a compound of the group A-1 and a compoundof the group B-1 or the combined use of a compound of the group A-2 anda compound of the group B-2 can increase the ionization potential of theelectrode layer effectively. It is therefore possible to obtain anorganic EL device which has excellent durability, a low driving voltage,and high luminescence intensity. The electrode layer configured thus isalso characterized by having an excellent etching property. Moreover,since at least one group out of the group A-1, the group A-2, the groupB-1, and the group B-2 includes chalcogenides of Si or nitrides of thesame in the electrode layer, it is possible to improve the adhesion ofthe electrode layer to the base member at the time of formation. Inaddition, the electrode layer can be formed with higher uniformity.

Incidentally, when the anode layer is made of these compounds, theionization potential is preferably given a value of 5.6 eV or higher inconsideration of hole injectability. When the cathode layer is made, onthe other hand, the ionization potential is preferably given a valuebelow 4.0 eV in consideration of electron injectability. The materialsmentioned in the present invention can achieve ionization potentials of5.8 eV or higher, being extremely suitable for the anode material.

Moreover, the organic EL device of the present invention is one in whichthe anode layer and cathode layer or either one of the electrode layershas a specific resistance lower than 1 Ω·cm. Such configuration makes itpossible to prevent the occurrence of uneven luminescence in the displayscreen due to high resistance of the electrode layer.

Consequently, the specific resistance of the electrode layer can thus berestricted to improve electron and hole injectabilities. A furtherreduction in the driving voltage of the organic EL device is alsopossible. Incidentally, if, in contrast, the constituent material of theelectrode layer has a specific resistance above 1 Ω·cm, a double-layerstructure is preferably used which includes an electrode layer made of aconstituent material having a specific resistance lower than 1 Ω·cm.

Moreover, the present invention is the organic EL device in which thecompound of the group A-1 or A-2 is any of chalcogenides or nitrides ofSn, In, and Zn. These compounds are particularly low in quenchingproperty among the compounds of the group A-1 or A-2, and thus capableof achieving an organic EL device which has high luminescence intensity.

Moreover, the present invention is the organic EL device in which thecompound of the group B-1 or B-2 is an oxide of any substance out of Ce,Nd, Sm, Eu, Tb, and Ho. These compounds can be used in combination tofacilitate adjusting the values of the ionization potential and the bandgap energy in the electrode layer independently.

Moreover, the present invention is the organic EL device in which thecontent of the compound of the group B-1 or B-2 falls within the rangeof 0.5 and 30 at. % with the total amount of the electrode layer as 100at. %. Setting the value in such a range can further facilitateadjusting the value of the ionization potential in the electrode layerwhile maintaining high transparency (light transmittance). Besides, theelectrode layer configured thus is characterized by having excellentetching properties to acids and the like.

Moreover, the present invention is the organic EL device in which theelectrode layer has a thickness within the range of 1 and 100 nm. Suchconfiguration makes it possible to obtain an organic EL device which hasmore excellent durability, a low driving voltage, and high luminescenceintensity. In addition, when the thickness of the electrode layer is insuch a range, the organic EL device is prevented from becomingexcessively thick.

Now, the organic EL device of the present invention is one in which aninorganic thin film layer containing at least one inorganic compoundselected from the foregoing group A-1 and at least one compound selectedfrom the group B-1 or an inorganic thin film layer containing at leastone compound selected from the foregoing group A-2 and at least onecompound selected from the group B-2 is arranged in both or eitherbetween the anode layer and the organic luminescent layer and/or betweenthe cathode layer and the organic luminescent layer.

Such additional arrangement of the inorganic thin film layer cansuppress leak current effectively, enhance the efficiency of the organicEL device, and improve the durability.

Incidentally, the inorganic thin film layer, when arranged between theanode layer and the organic luminescent layer, is extremely preferablygiven a composition different from those of the anode layer and theorganic thin film layer. Specifically, when the anode layer is made of acompound comprising a group A-1 compound/a group B-1 compound=70 to 90at. %/0.5 to 10 at. %, it is preferable that the inorganic thin filmlayer be made of a compound comprising a group A-1 compound/a group B-1compound=50 to below 90 at. %/above 10 at. % to 50 at. %. The same holdsfor the case of using the compounds of the groups A-2 and B-2.

Moreover, the organic EL device of the present invention is one in whichthe organic luminescent layer contains at least one aromatic compoundhaving a styryl group whose structural formula is given by any of thefollowing general formulae (chemical formula 2-1) to (chemical formula2-3):

where in the general formula (chemical formula 2-1), Ar¹ is an aromaticgroup having 6 to 40 carbon atoms, each of Ar², Ar³, and Ar⁴ is hydrogenor an aromatic group having 6 to 40 carbon atoms, at least one of Ar¹,Ar², Ar³, and Ar⁴ is an aromatic group, and the condensation number n isan integer of 1 to 6;

where in the general formula (chemical formula 2-2), Ar⁵ is an aromaticgroup having 6 to 40 carbon atoms, each of Ar⁶ and Ar⁷ is hydrogen or anaromatic group having 6 to 40 carbon atoms, at least one of Ar⁵, Ar⁶,and Ar⁷ is substituted with a styryl group, and the condensation numberm is an integer of 1 to 6; and

where in the general formula (chemical formula 2-3), Ar⁸ and Ar¹⁴ areeach an aromatic group having 6 to 40 carbon atoms, each of Ar⁹ to Ar¹³is hydrogen or an aromatic group having 6 to 40 carbon atoms, at leastone of Ar⁸ to Ar¹⁴ is substituted with a styryl group, and thecondensation numbers p, q, r, and s are 0 or 1 each.

The present invention also is a method of fabricating the organic ELdevice described so far, comprising the steps of: forming the electrodelayer by sputtering; and forming the organic luminescent layer by vacuumdeposition. In this way of formation, it is possible to form a holeinjection layer and an organic luminescent layer which are dense andhave uniform film thicknesses. It is thus possible to provide an organicEL device having yet uniform luminescence intensity.

Third Group of Invention

To solve the foregoing problems, the aspect of a third group of theinvention adopts the following means.

Invention of an Electrode Substrate for an Organic EL Device

1. Initially, the present invention is an electrode substrate for anorganic EL device, comprising an electrode for driving an organicelectroluminescence layer and a base member, wherein the electrode ismade of a laminate of the following two layers:

(1) a thin film layer of a metal oxide having a work function above 5.6eV in value; and

(2) a thin film layer composed mainly of Ag.

Now, when the multilayer-film configuration is employed, the outermostlayer or the surface to contact the organic luminescent layer must be ametal oxide layer. The reason is that such effects as lower voltage,enhanced luminescence intensity, and improved durability are small.

The means described above can be adopted to make the outermost layer orthe surface to contact the organic luminescent layer a metal oxidelayer.

Here, the work function is set at 5.6 eV or higher for the reason thatsuch effects as lower voltage, enhanced luminescence intensity, andimproved durability are small unless this condition is satisfied.

2. Next, the present invention is the electrode substrate for an organicEL device, characterized in that the thin film layer of the metal oxidehas a work function of 5.8 eV or higher.

As described above, the work function must be 5.6 eV or higher, and ispreferably 5.8 eV or higher.

Note that this value is a measurement in the air after film formation, avalue before the application of UV cleaning or the like (pre-cleaningvalue). This work function was measured with “AC-1” from Rikagaku GikenCo., Ltd., by using a photoemission method. The measurement samples wereirradiated with light of 3.5 to 6.5 eV, and electrons emitted from thesamples were measured. The work function is determined from theirradiation light energy required to emit electrons.

3. Next, the present invention is the foregoing electrode substrate,characterized in that the thin film layer of the metal oxide: iscomposed mainly of indium oxide; and contains at least one or more typesof metal oxides selected from the group consisting of niobium oxide,hafnium oxide, tantalum oxide, and a lanthanide metal oxide.

4. Furthermore, the foregoing electrode substrate is characterized inthat the thin film layer of the metal oxide contains zinc oxide or tinoxide as a main component thereof along with indium oxide.

As above, the present invention contains indium oxide as a maincomponent of the thin film layer of the metal oxide. It also containszinc oxide and/or tin oxide.

For example, when indium oxide+zinc oxide are the main components,In/(In+Zn)=0.5% to 0.95% by atom is desirable. Here, In/(In+Zn)indicates the ratio of indium atoms to the total sum of the numbers ofindium atoms and zinc atoms in the thin film layer of the metal oxide.

The value of the foregoing ratio In/(In+Zn) is preferably 0.7 to 0.9,and yet preferably 0.8 to 0.9. The reason is that if this value is below0.5, the thin film layer of the metal oxide can drop in conductivity.Above 0.95, on the other hand, the etching property might deteriorate.

Moreover, when, for example, indium oxide+tin oxide are the maincomponents, In/(In+Sn)=0.7% to 0.95% by atom is desirable. Here,In/(In+Sn) indicates the ratio of indium atoms to the total sum of thenumbers of indium atoms and tin atoms in the thin film layer of themetal oxide.

The value of the foregoing ratio In/(In+Sn) is preferably 0.8 to 0.95,and yet preferably 0.85 to 0.95. The reason is that if this value isbelow 0.7 or above 0.95, the thin film layer of the metal oxide can dropin conductivity.

Now, the amount of niobium oxide, hafnium oxide, tantalum oxide, and alanthanide metal oxide to be added is 0.1% to below 20% by atom,preferably 1% to below 10% by atom, and yet preferably 1% to below 5% byatom with respect to the total metal atoms. The reason is that atamounts of addition below 0.1% by atom, the effect of the addition willnot reach a significant level, sometimes failing to increase the workfunction to or above 5.6 eV. On the other hand, at amounts of additionof 20% and higher by atom, the thin film of the metal oxide becomes aninsulative film with the problem of a drop in conductivity.

5. Moreover, the present invention is the foregoing electrode substrate,characterized in that the lanthanide metal oxide is at least one or moretypes of metal oxides selected from the group consisting of ceriumoxide, praseodymium oxide, neodymium oxide, samarium oxide, and terbiumoxide.

Incidentally, in the present invention, this multilayer filmconstituting an electrode preferably has a surface resistance below 10Ω/sq. Preferably below 6 Ω/sq., and yet preferably 4 Ω/sq.

6. Moreover, the present invention is the foregoing electrode substrate,characterized in that the thin film layer composed mainly of Ag containsmetal having a work function of 5.0 eV or higher.

7. Furthermore, the present invention is characterized in that the metalhaving a work function of 5.0 eV or higher contains one type or two ormore types of metal selected from the Au, Ir, Ni, Pd, and Pt.

As in these inventions 6 and 7, the addition of metal having a workfunction of 5.0 eV or higher enhances the stability of the Ag layer. Theamount of addition is 0.01 to 5 wt % or lower, preferably 0.1 to 2 wt %,and yet preferably 1 to 2 wt %.

The reason for this is that at amounts of addition below 0.01, theeffect of the addition is small. On the other hand, at amounts ofaddition above 5 wt %, the Ag thin film layer may drop in conductivityor become expensive.

Moreover, other metals (such as Cu, Co and Zr) may be added as a thirdcomponent without affecting stability, resistance, and reflectance.

When the present invention is used to constitute an organic EL devicesuch as an organic EL device, it is preferable to employ thicknesses asfollows:

(1) In the Case of Outputting Light Through the Anode

In this case, the “thin film layer composed mainly of Ag” (sometimesreferred to simply as an Ag thin film) is given a thickness of 3 to 15nm, and preferably 5 to 10 nm. The reason is that if the Ag thin filmhas a thickness below 3 nm, the anode might not be reduced inresistance. On the other hand, when the Ag thin film has a thicknessabove 15 nm, the transmittance can fall with a drop in the light outputefficiency from the luminescent layer.

Moreover, the thin film layer of the metal oxide (sometimes referred tosimply as an oxide layer) may have a thickness selected from the rangeof 10 to 200 nm so as to suppress reflection from the Ag layer. Thethickness of this oxide layer is preferably selected from the range of20 and 50 nm, and yet preferably 25 and 40 nm. When this oxide layer hasa thickness below 10 nm, the stabilization of the Ag layer might not beachieved, with the result of lower durability of the organic EL device.On the other hand, when this oxide layer has a thickness above 200 nm,the transmittance can fall with a drop in the light output efficiency.

(2) In the Case of Outputting Light Through the Cathode

In this case, the Ag layer may be a thick film in order to reflect thelight coming from the luminescent layer toward the cathode. The Ag layerhas a thickness in the range of 30 and 300 nm, preferably 50 and 250 nm,and yet preferably 100 and 200 nm.

When this Ag layer is given a thickness of 300 nm or greater, it becomestoo thick and can cause a leak current at the electrode end. Incontrast, when the Ag layer has a thickness below 30 nm, the function ofreflecting light toward the cathode may become weaker. With theobjective of exercising the reflecting function of this Ag layer, thethickness of this Ag layer is desirably set at 30 nm or greater, andpreferably 50 nm or greater.

Invention of an Organic EL Device

The following describes the invention of an organic EL device having thesame characteristics as those of the electrode substrate for an organicEL device described above. These have the same functions as those of theelectrode substrate for an organic EL device described above.

To achieve the foregoing object, the present invention is an organic ELdevice having a structure that at least an anode layer, an organicelectroluminescence layer, and a cathode layer are laminated, whereineither one or both of the electrodes, i.e., the anode layer and thecathode layer are made of a laminate of a thin film layer of a metaloxide having a work function above 5.6 eV and a thin film layer composedmainly of Ag.

The present invention is also characterized in that the thin film layerof the metal oxide has a work function of 5.8 eV or higher.

The present invention is also characterized in that the thin film layerof the metal oxide: is composed mainly of indium oxide; and contains atleast one or more types of metal oxides selected from the groupconsisting of niobium oxide, hafnium oxide, tantalum oxide, and alanthanide metal oxide.

The present invention is also characterized in that the thin film layerof the metal oxide contains zinc oxide or tin oxide as a main componentthereof along with indium oxide.

The present invention is also characterized in that the lanthanide metaloxide is at least one or more types of metal oxides selected from thegroup consisting of cerium oxide, praseodymium oxide, neodymium oxide,samarium oxide, and terbium oxide.

The present invention is also characterized in that the thin film layercomposed mainly of Ag contains metal having a work function of 5.0 eV orhigher.

The present invention is also characterized in that the metal having awork function of 5.0 eV or higher contains one type or two or more typesof metal selected from Au, Ir, Ni, Pd, and Pt.

Invention of a Method of Fabricating an Organic EL Device

The present invention also is a method of fabricating the organic ELdevice described above, comprising the steps of: forming the electrodeby sputtering; and forming the organic electroluminescence layer byvacuum deposition.

Fourth Group of Invention

To solve the foregoing problems, the aspect of a fourth group of theinvention adopts the following means.

1. Initially, the present invention is an electrode substrate for anorganic EL device, comprising an electrode for driving an organicelectroluminescence layer and a base member, wherein the electrode is alaminate comprising an anode thin film layer of a metal oxide having awork function above 5.6 eV and a metal thin wire.

Here, the work function is set at 5.6 eV or higher for the reason thatsuch effects as lower voltage, enhanced luminescence intensity, andimproved durability might be smaller unless this condition is satisfied.

Besides, without the metal thin wire, the anode can grow in electroderesistance and increase in work function, possibly limiting the effectssuch as enhanced luminescence intensity.

2. Next, the present invention is characterized in that the anode thinfilm layer of the metal oxide is one having a work function of 5.8 eV orhigher.

As described above, the work function must be 5.6 eV or higher, and ispreferably 5.8 eV or higher. Incidentally, this value is a valuemeasured in the air with AC-1 from Rikagaku Giken, after UV cleaning.

3. Next, the present invention is characterized in that the anode thinfilm layer of the metal oxide: is composed mainly of indium oxide, andalso contains zinc oxide and/or tin oxide as a main component(s)thereof; and further contains a lanthanide metal oxide.

The addition of the lanthanide can effectively give the thin film layerof the metal oxide composed mainly of indium oxide, zinc oxide, and/ortin oxide a work function of 5.6 eV or higher.

In the cases of metals other than those mentioned above as maincomponents, the amount of addition of lanthanides must be increased inorder to set the work function at or above 5.6 eV effectively. A rise inthe amount of addition, however, can increase the resistance, decreasethe transmittance, and deteriorate the etching property.

4. Next, the present invention is characterized in that the foregoinglanthanide metal oxide is a single metal oxide or two or more metaloxides selected from cerium oxide, praseodymium oxide, neodymium oxide,samarium oxide, and terbium oxide.

For example, when indium oxide+zinc oxide are the main components,In/(In+Zn)=0.5% to 0.98% by atom is preferable. The value of theforegoing ratio In/(In+Zn) is preferably 0.7 to 0.95, and yet preferably0.8 to 0.9. The reason is that if this value is below 0.5, the metaloxide film can drop in conductivity. Above 0.98, on the other hand, theetching property might deteriorate.

Moreover, when, for example, indium oxide+tin oxide are the maincomponents, In/(In+Sn)=0.7% to 0.98% by atom is desirable.

The value of the foregoing ratio In/(In+Sn) is preferably 0.8 to 0.95,and yet preferably 0.85 to 0.95. The reason is that if this value isbelow 0.7 or above 0.98, the thin film layer of the metal oxide can dropin conductivity.

When, for example, indium oxide+tin oxide+zinc oxide are the maincomponents, In/(In+Sn+Zn)=0.5% to 0.98% by atom is desirable.

The value of the foregoing ratio In/(In+Sn+Zn) is preferably 0.7 to0.95, and yet preferably 0.8 to 0.95. The reason is that if this valueis below 0.5, the metal oxide film can drop in conductivity. Above 0.98,the etching property might deteriorate.

Now, the amount of the lanthanide metal oxide to be added is desirably0.1% to below 20% by atom, preferably 1% to below 10% by atom, and yetpreferably 1% to below 5% by atom with respect to the total metal atoms.The reason is that if this value is below 0.1% by atom, the additionmight not produce any effect, failing to achieve a work function of 5.6eV or higher. Above 20% by atom, the thin film can increase inresistance with a drop in conductivity.

Moreover, the thin film layer desirably has a thickness of 10 to 500 nm,preferably 30 to 300 nm, and yet preferably 30 to 200 nm. The reason isthat if this value is 10 nm or smaller, a problem might occur in themechanical strength of the thin film layer. At or above 500 nm, therecan occur a problem in etching property and an increase in the filmforming time.

The oxygen partial pressure at the time of film formation should be setat 0-5%. Preferably it is set at 0-2%, and yet preferably at 0-1%. Thereason is that if this value is 5% or higher, the resistance canincrease.

As for crystallinity, the anode layer is desirably amorphous. The reasonis that when the anode layer has an amorphous crystallinity, residuesdisappear from the end faces at the time of etching (etching surfaces)and the electrodes can be tapered to resolve such troubles asdisconnection of opposed electrodes.

5. The present invention is the foregoing substrate for an organic ELdevice, characterized in that the metal thin wire is composed mainly ofany of Ag, Al, and Cu.

6. The present invention is the foregoing substrate for an organic ELdevice, characterized in that metal having a work function of 5.0 eV orhigher is added to the metal thin wire.

7. The present invention is the foregoing substrate for an organic ELdevice, characterized in that the metal having a work function of 5.0 eVor higher contains one type or two or more types of metal selected fromAu, Ir, Ni, Co, Pd, and Pt.

The addition of the metal having a work function of 5.0 or higherenhances the stability of the metal thin wire. The amount of addition is0.01 to 5 wt % or lower, preferably 0.1 to 2 wt %, and yet preferably0.5 to 2 wt %. The reason is that if this value is below 0.01, theeffect of addition is small. With addition of above 5 wt %, the Ag thinfilm layer and the like may drop in conductivity or become expensive.

Moreover, other metals may be added as a third component withoutaffecting stability and resistance.

The metal thin wire desirably has a thickness of 10 to 500 nm, andpreferably 20 to 400 nm. The reason is that if this value is below 10nm, there may occur the problem that the anode resistance will notdecrease. Above 500 nm, an increased difference in level betweenelectrodes can sometimes cause a leak current.

The width of the metal thin wire (in the minor-side direction) must berendered smaller than the width of the anode thin film layer (in theminor-side direction). The width of the metal thin wire (in theminor-side direction) is 2-40%, preferably 3-30%, and yet preferably4-25% the width of the anode thin film layer.

8. The present invention is the foregoing electrode substrate for anorganic EL device, comprising a protective film on the anode thin filmlayer of the metal oxide. The reason is that the provision of theprotective film improves the durability of the metal thin wire.

The protective layer is desirably made of material capable of beingetched in the etchant of the metal thin wire, and has conductivity. Anamorphous transparent conductive film made of indium oxide-zinc oxidecan be suitably used as such material. In that case, indium may be usedat the ratio of In/(In+Zn)=0.2 to 0.98, preferably 0.5 to 0.95, and yetpreferably 0.7 to 0.9.

9. The present invention is a method of fabricating an electrodesubstrate for an organic EL device, comprising the steps of: laminatingan anode thin film layer of the metal oxide on a base member, and thenlaminating a metal thin film layer made of a metal thin wire thereon;etching the metal thin film layer in a mixed acid of phosphoric acid,nitric acid, and acetic acid; and after the etching, performingadditional oxalic-acid etching to pattern the anode thin film layer.

10. Moreover, the present invention is the method of fabricating anelectrode substrate for an organic EL device, characterized in that thebase member is a glass substrate.

Here, the anode thin film layer can be etched in an etchant containingoxalic acid. The concentration of oxalic acid is 1 to 20 wt % of theaqueous solution, preferably 2 to 10 wt % of the aqueous solution, andyet preferably 2 to 5 wt %. The reason is that at or below 1 wt %, asufficient etching rate cannot be achieved. At or above 20 wt %, thecrystal of oxalic acid may be precipitated. In addition, acids in nodanger of corroding metal may also be added.

The metal-etching acids are not limited to any particular ones, but maybe any acids as long as they cause no damage on the anode thin filmlayer. A mixed acid of phosphoric acid, nitric acid, and acetic acid canbe used yet effectively. The ratios of mixture of the respective acidsare not particularly restricted. Nevertheless, such mixture as allows asufficient etching rate of the metal thin film and causes no damage onthe anode thin film layer is naturally preferable. No particularrestriction is imposed on the concentrations, either. Nevertheless, suchconcentrations as allow a sufficient etching rate of the metal thin filmand cause no damage on the anode thin film layer are naturallypreferable. Thus, water dilution is also desirable if needed.

11. An organic EL device uses an electrode substrate for an organic ELdevice, the electrode substrate comprising an electrode for driving anorganic electroluminescence layer and a base member, the electrode beinga laminate comprising an anode thin film layer of a metal oxide having awork function above 5.6 eV and a metal thin wire, the organic EL deviceincluding: the organic electroluminescence layer; and a cathode layeropposed to the electrode.

Here, the organic EL device provides the same functions and effects asthose of the electrode substrate for an organic EL device describedabove.

Fifth Group of Invention

Hereinafter, the aspect of a fifth group of invention will be described.This fifth group will be detailed mainly in a fifth embodiment to beseen later.

1. The present invention is a substrate for an organic EL device,comprising a laminate of: an electrode for driving the organicelectroluminescence layer descried above; a transparent conductive thinfilm containing indium oxide; a metal thin wire; and a thin film layerof a metal oxide, the laminate being formed in this order on a basemember, wherein the thin film layer of the metal oxide has a workfunction above 5.6 eV and a specific resistance of 10 E+4 Ωcm or higher.

The reason is that the work function of 5.6 eV or higher improves thehole injection efficiency to organic materials, enhances luminescenceintensity, and extends life. The work function is preferably 5.8 eV orhigher, and yet preferably 6.0 eV or higher.

Moreover, the thin film layer of the metal oxide has a thickness of 1 to100 nm, preferably 5 to 50 nm, and yet preferably 5 to 20 nm. If thethickness of the thin film layer is 1 nm or smaller, the thin film layermay not produce any effect. If the thickness of the thin film layer is100 nm or greater, the inter-anode resistance of the thin film layerdecreases, possibly causing crosstalk.

The areas of the electrode substrate for the thin film layer to coverare a display area and/or a wiring area. An external electrode outletmay or may not be covered.

2. The present invention is a substrate for an organic EL device,comprising a laminate of: an electrode for driving the organicelectroluminescence layer descried above; a metal thin wire; atransparent conductive thin film containing indium oxide; and a thinfilm layer of the metal oxide, the laminate being formed in this orderon a base member, wherein the thin film layer of the metal oxide has awork function above 5.6 eV and a specific resistance of 10 E+4 Ωcm orhigher.

The present invention is the invention set forth in 1 above, theconfiguration of which is changed in order. That is, the order oflamination of the transparent conductive thin film containing indiumoxide and the metal thin wire is inverted. Even in such a configuration,the functions and effects of the invention are the same as in 1 above.

3. The present invention is characterized in that the thin film layer ofthe metal oxide has a work function within the range of 10 E+4 Ωcm and10 E+8 Ωcm.

The reason is that if the specific resistance is 10 E+4 Ωcm or lower,the inter-anode resistance decreases to cause crosstalk. Moreover, ifthe specific resistance is 10 E+8 Ωcm or higher, the resistance becomesso high that the hole injection efficiency may drop.

4. The present invention is characterized in that a thin film layer ofthe metal oxide layer has a work function of 5.8 eV or higher.

As described above, the work function is preferably 5.8 eV or higher,and yet preferably 6.0 eV or higher.

5. The present invention is characterized in that the metal oxidecontains at least either one of zinc oxide and tin oxide.

With main components of indium oxide+tin oxide type, In/(In+Sn)=0.6 to0.98 at % is preferable. Yet preferably 0.75 to 0.95 at %.

With indium oxide+zinc oxide+tin oxide type, In/(In+Zn+Sn)=0.6 to 0.98at % is preferable. Yet preferably 0.75 to 0.95 at %. Here, at % meanspercents by atom.

6. The present invention is characterized in that the metal oxidecontains at least one type of lanthanide oxide.

The content of the lanthanide metal oxide is 5 to 50 at %, andpreferably 10 to 40 at %, with respect to the total metal atoms. Yetpreferably 10 to 30 at %. The reason is that if the content of thelanthanide metal oxide is below 5 at %, the resistance can fall with adrop in the work function. Moreover, if the content of the lanthanidemetal oxide exceeds 50 at %, the film can become insulative, possiblyreducing the work function. Here, at % means percents by atom.

As above, it is desirable that the metal oxide includes indium oxide,zinc oxide, and/or tin oxide, and contains a lanthanide metal oxide.

7. The present invention is characterized in that the lanthanide metaloxide is an oxide selected from the group consisting of cerium oxide,praseodymium oxide, neodymium oxide, samarium oxide, and terbium oxide.

8. The present invention is characterized in that the metal thin wirecontains at least one selected from the group consisting of Ag, Al, andCu.

The metal thin wire is desirably made of metal having a specificresistance below 10 μΩcm. The use of Ag, Al, and Cu is particularlydesirable.

9. The present invention is characterized in that the metal thin wirecontains metal having a work function of 5.0 eV or higher.

For the sake of stabilization of Ag, Al, and Cu which are used as themain components of the metal thin wire, metal having a work function of5.0 eV or higher is desirably added.

10. The present invention is characterized in that the metal having awork function of 5.0 eV or higher contains one type or two or more typesof metal selected from the group consisting of Au, Ir, Ni, Co, Pd, andPt.

As above, Au, Ir, Ni, Co, Pd, and Pt are desirably used as the metalhaving a work function of 5.0 eV or higher. Incidentally, metals otherthan the foregoing ones are also preferably added without adverselyaffecting the performance of the metal thin wire. Examples thereofinclude such metals as Mo and Zr.

Moreover, while the etchant of these metals is not limited to anyparticular one, it is desirable to select an etchant that causes nodamage on the underlying transparent conductive thin film. An examplethereof is a mixed acid of phosphoric acid-acetic acid-nitric acid.Incidentally, sulfonic acid, polysulfonic acid, and the like may beadded to this mixed acid.

The metal layer made of this metal thin wire need not be a single layer.The metal layer may be sandwiched between different metals. Examples ofthe different metals include such metals as Ti, Cr, Mo, In, and Zn.

Concrete examples of the metal thin wire sandwiched between differentmetals include Ti/Al/Ti, Cr/Al/Cr, Mo/Al/Mo, In/Al/In, Zn/Al/Zn, andTi/Ag/Ti.

11. The present invention is an organic EL device comprising: theelectrode substrate for an organic EL device set forth in any of 1 to 10above; a cathode layer; and an organic electroluminescence layer.

Here, the organic EL device provides the same functions and effects asthose of the electrode substrate for an organic EL device describedabove.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing a table which shows the compositions ofsputtering targets in practical examples 1-1 to 1-9 and comparativeexamples 1-1 to 1-3;

FIG. 2 is a diagram showing a table which shows the characteristics ofconductive thin films fabricated by using the sputtering targets in thepractical examples 1-1 to 1-9 and the comparative examples 1-1 to 1-3;

FIG. 3 is a sectional view of an organic EL device in an embodiment 2-1;

FIG. 4 is a sectional view of an organic EL device in an embodiment 2-2;

FIG. 5 is a sectional view of an organic EL device in an embodiment 2-3;

FIG. 6 is a sectional view of an organic EL device in an embodiment 2-4;

FIG. 7 is a perspective view of a vacuum evaporator in an embodiment2-5;

FIG. 8 is a sectional view of the vacuum evaporator in the embodiment2-5;

FIG. 9 is a diagram for use in explaining measuring points on asubstrate;

FIG. 10 is a sectional view of an electrode substrate in the presentembodiment;

FIG. 11 is a sectional view of an organic EL device in the presentembodiment;

FIG. 12 is a series of sectional views of the process for fabricatingthe electrode substrate in the present embodiment;

FIG. 13 is a sectional view of an electrode substrate in the presentembodiment;

FIG. 14 is a sectional view of an organic EL device in the presentembodiment;

FIG. 15 is a series of sectional views of the process for fabricatingthe electrode substrate in the present embodiment;

FIG. 16 is a sectional view of an electrode substrate in the presentembodiment;

FIG. 17 is a sectional view of another type of electrode substrate inthe present embodiment;

FIG. 18 is a sectional view of an organic EL device in the presentembodiment; and

FIG. 19 is a diagram showing the chemical formulae of varioussubstances.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described inthe concrete with reference to the drawings. Incidentally, the referencedrawings schematically show the sizes, shapes, and arrangements of theindividual components to an extent that this invention becomes apparent,the ratios among the individual parts being different from in actualdevices and the like. Hence, this invention is not limited to the shownexamples alone. In the drawings, hatching for showing a section maysometimes be omitted.

Group of Embodiments 1

Hereinafter, a group of embodiments 1 of the present invention will bedescribed with reference to the drawings.

In the present embodiment, indium oxide, zinc oxide, and tin oxidepowders were mixed in predetermined proportions. In addition, apredetermined amount of cerium oxide, samarium oxide, europium oxide,terbium oxide, or bismuth oxide powder was measured and mixed therein asa third component. This mixture was ground in a wet grinder for 48hours, and then dry granulated and press molded before it was sinteredat 1380-1480° C. into a sintered article. This sintered articlecorresponds to an example of the sputtering target in claims.

Moreover, when the mixture is of indium oxide and zinc oxide, it containa hexagonal layered compound comprising indium oxide and zinc oxide(In₂O₃(ZnO)m: where m is an integer of 2 to 20). For instance, inpractical examples 1-1 to 1-6 to be described later, the inclusion ofsuch a hexagonal layered compound comprising indium oxide and zinc oxide(In₂O₃(ZnO)m: where m is an integer of 2 to 20) seems to achieve afurther reduction in resistance.

This sintered article was cut into a 4-inch φ5-mm(t) plate, which wasbonded by metal indium to a backing plate of oxygen-free copper toconstitute a sputtering target. In the present patent, the sputteringtarget, such as a sintered article, bonded to a backing plate will alsobe referred to as a “sputtering target.”

In the present embodiment, a plurality of types of sputtering targetshaving different compositions were made. The table of FIG. 1 shows thecompositions of the respective sputtering targets of the plurality oftypes.

Practical Examples 1-1 to 1-5

As shown in the table of FIG. 1, practical examples 1-1 to 1-5 areexamples where tin oxide is 0 in ratio. The practical examples 1-1 to1-5 are, then, sputtering targets having indium of approximately 93% byatom and zinc of approximately 17% by atom. Note that in the table ofFIG. 1, the composition ratios of indium, zinc, and tin, as is evidentfrom the shown expressions, are ones with respect to the total sum ofindium, zinc, and tin, not ones with respect to the total amount of thesputtering target.

In the practical example 1-1, a predetermined amount of cerium oxidepowder is further added to the composition having indium ofapproximately 93% by atom and zinc of approximately 17% mentioned above.As a result, the sputtering target of the practical example 1-1 containscerium (Ce) of 3% by atom.

In the practical example 1-2, a predetermined amount of cerium oxidepowder is further added to indium of approximately 93% by atom and zincof approximately 17% mentioned above. As a result, the sputtering targetof the practical example 1-2 contains cerium (Ce) of 6% by atom.

In the practical example 1-3, a predetermined amount of samarium oxidepowder is further added to indium of approximately 93% by atom and zincof approximately 17% mentioned above. As a result, the sputtering targetof the practical example 1-3 contains samarium (Sm) of 5% by atom.

In the practical example 1-4, a predetermined amount of europium oxidepowder is further added to indium of approximately 93% by atom and zincof approximately 17% mentioned above. As a result, the sputtering targetof the practical example 1-4 contains europium (Eu) of 10% by atom. Asabove, in these practical examples, cerium, samarium, and europium areshown as examples of lanthanides. Needless to say, other lanthanides mayalso be used.

In the practical example 1-5, a predetermined amount of bismuth oxidepowder is further added to indium of approximately 93% by atom and zincof approximately 17% mentioned above. As a result, the sputtering targetof the practical example 1-5 contains bismuth (Bi) of 6% by atom.

Practical Examples 1-6 to 1-9

As shown in the table of FIG. 1, a practical example 1-6 is an examplewhere indium oxide, zinc oxide, and tin oxide powders are all mixed.

The practical example 1-6 is a sputtering target having indium ofapproximately 89% by atom, zinc of approximately 6% by atom, and tin ofapproximately 5% by atom. A predetermined amount of hafnium oxide powderis added further. As a result, the sputtering target of the practicalexample 1-6 contains hafnium (Hf) of 5% by atom.

A practical example 1-7 is an example where zinc oxide is 0 in ratio.Then, the example is a mixture of indium oxide and tin oxide. Thepractical example 1-7 is a sputtering target having indium ofapproximately 91% by atom and tin of approximately 9% by atom. Apredetermined amount of tantalum oxide powder is added further. As aresult, the sputtering target of the practical example 1-7 containstantalum (Ta) of 5% by atom.

A practical example 1-8 is a sputtering target having indium ofapproximately 91% by atom and tin of approximately 9% by atom. Apredetermined amount of terbium oxide powder is added further. As aresult, the sputtering target of the practical example 1-8 containsterbium (Tb) of 5% by atom.

A practical example 1-9 is a sputtering target of 100% indium oxide. Apredetermined amount of cerium oxide powder is added further. As aresult, the sputtering targets of the practical examples 1-9 eachcontain cerium (Ce) of 6% by atom.

The sputtering targets made thus were used in an RF magnetron sputteringsystem to form films on a glass substrate (#7059 from Corning, Inc.) anda polyethylene terephthalate film substrate from Toray Industries, Inc.

The table of FIG. 2 shows measurements on the physical properties of thethin films fabricated thus. The table shown in FIG. 2 is one showing thevalues of the transparency and work functions of conductive films, theconductive films being fabricated by using the sputtering targets of theforegoing practical examples 1-1 to 1-9 and comparative examples 1-1 to1-3. This table also shows the physical properties of the sputteringtargets themselves in the foregoing practical examples 1-1 to 1-9 andthe comparative examples 1-1 to 1-3.

Initially, as shown in this table, the sputtering target of thepractical example 1-1 has a density of 6.62 g/cc and a bulk resistivityof 2.3 mΩ·cm. The thin film formed on the glass substrate by using thesputtering target of this practical example 1-1 exhibited a resistivityof 960 μΩ·cm and a transparency of 89%. Besides, the work function was5.72 eV. As for the etching characteristic, residues were not observedat all. Moreover, the thin film formed on the film substrate by usingthe sputtering target of this practical example 1 exhibited aresistivity of 980 μΩ·cm and a transparency of 87%. Besides, the workfunction was 5.55 eV.

Incidentally, the resistivities of the thin films were measured by thefour probe method (Loresta: from Mitsubishi Petrochemical Co., Ltd.).Moreover, the transparencies were transmittances at a wavelength of 550nm. The work functions were measured by AC-1 from Riken Keiki Co., Ltd.For the etching characteristics, the mark “double circle” in the tablemeans no residue at all, the mark “circle” little residue, the mark“triangle” a slight amount of residues, and the mark “cross” a largeamount of residues or that etching was impossible. The same also holdsfor the following descriptions.

In the practical example 1-2, the sputtering target has a density of6.71 g/cc and a bulk resistivity of 0.87 mΩ·cm. The thin film formed onthe glass substrate by using the sputtering target of this practicalexample 1-2 exhibited a resistivity of 1850 μΩ·cm and a transparency of90%. Besides, the work function was 5.62 eV. As for the etchingcharacteristic, residues were not observed at all. Moreover, the thinfilm formed on the film substrate by using the sputtering target of thispractical example 1-2 exhibited a resistivity of 1880 μΩ·cm and atransparency of 89%. Besides, the work function was 5.93 eV.

In the practical example 1-3, the sputtering target has a density of6.76 g/cc and a bulk resistivity of 1.03 mΩ·cm. The thin film formed onthe glass substrate by using the sputtering target of this practicalexample 1-3 exhibited a resistivity of 750 μΩ·cm and a transparency of88%. Besides, the work function was 6.03 eV. As for the etchingcharacteristic, residues were not observed at all. Moreover, the thinfilm formed on the film substrate by using the sputtering target of thispractical example 1-3 exhibited a resistivity of 810 μΩ·cm and atransparency of 87%. Besides, the work function was 5.93 eV.

In the practical example 1-4, the sputtering target has a density of6.81 g/cc and a bulk resistivity of 2.4 mΩ·cm. The thin film formed onthe glass substrate by using the sputtering target of this practicalexample 1-4 exhibited a resistivity of 460 μΩ·cm and a transparency of89%. Besides, the work function was 5.78 eV. As for the etchingcharacteristic, residues were not observed at all. Moreover, the thinfilm formed on the film substrate by using the sputtering target of thispractical example 1-4 exhibited a resistivity of 610 μ∩·cm and atransparency of 88%. Besides, the work function was 5.73 eV.

In the practical example 1-5, the sputtering target has a density of6.93 g/cc and a bulk resistivity of 0.82 mΩ·cm. The thin film formed onthe glass substrate by using the sputtering target of this practicalexample 1-5 exhibited a resistivity of 880 μΩ·cm and a transparency of87%. Besides, the work function was 5.63 eV. As for the etchingcharacteristic, residues were not observed at all. Moreover, the thinfilm formed on the film substrate by using the sputtering target of thispractical example 1-5 exhibited a resistivity of 960 μΩ·cm and atransparency of 87%. Besides, the work function was 5.61 eV.

In the practical example 1-6, the sputtering target has a density of6.95 g/cc and a bulk resistivity of 0.96 mΩ·cm. The thin film formed onthe glass substrate by using the sputtering target of this practicalexample 1-6 exhibited a resistivity of 670 μΩ·cm and a transparency of88%. Besides, the work function was 5.62 eV. As for the etchingcharacteristic, residues were not observed at all. Moreover, the thinfilm formed on the film substrate by using the sputtering target of thispractical example 1-6 exhibited a resistivity of 750 μΩ·cm and atransparency of 88%. Besides, the work function was 5.60 eV.

In the practical example 1-7, the sputtering target has a density of6.92 g/cc and a bulk resistivity of 0.72 mΩ·cm. The thin film formed onthe glass substrate by using the sputtering target of this practicalexample 1-7 exhibited a resistivity of 540 μΩ·cm and a transparency of89%. Besides, the work function was 6.20 eV. As for the etchingcharacteristic, residues were not observed at all. Moreover, the thinfilm formed on the film substrate by using the sputtering target of thispractical example 1-7 exhibited a resistivity of 540 μΩ·cm and atransparency of 88%. Besides, the work function was 6.17 eV.

In the practical example 1-8, the sputtering target has a density of6.91 g/cc and a bulk resistivity of 1.05 mΩ·cm. The thin film formed onthe glass substrate by using the sputtering target of this practicalexample 1-8 exhibited a resistivity of 840 μΩ·cm and a transparency of89%. Besides, the work function was 6.20 eV. At the time of etching,residues were not observed at all. The thin film formed on the filmsubstrate by using the sputtering target of this practical example 1-8exhibited a resistivity of 860 μΩ·cm and a transparency of 88%. Besides,the work function was 5.61 eV.

In the practical example 1-9, the sputtering target has a density of6.78 g/cc and a bulk resistance of 2.8 mΩ·cm. The thin film formed onthe glass substrate by using the sputtering target of this practicalexample 1-9 exhibited a resistivity of 1250 μΩ·cm and a transparency of89%. Besides, the work function was 5.68 eV. As for the etchingcharacteristic, residues were not observed at all. The thin film formedon the film substrate by using the sputtering target of this practicalexample 1-9 exhibited a resistivity of 1450 μΩ·cm and a transparency of88%. Besides, the work function was 5.66 eV.

When evaluated for crystallinity through an X-ray analysis, the thinfilms of these practical examples 1-1 to 1-9 showed no peak, confirmingthat all were amorphous.

As described above, according to these practical examples, it ispossible to obtain a conductive film of high work function whilemaintaining high transparency.

Next, the three types of comparative examples were also sputtered intothin films as in the foregoing practical examples. Then, the physicalproperties of the formed thin films are also shown in the table of FIG.2.

As shown in the table of FIG. 2, the sputtering target of thecomparative example 1-1 has a density of 6.65 g/cc and a bulkresistivity of 2.5 mΩ·cm. The sputtering target of this comparativeexample 1-1 was used to form a thin film on the glass substrate as inthe foregoing practical examples. This thin film was 380 μΩ·cm inresistivity and 89% in transparency. The work function was 5.22 eV. Asfor the etching characteristic, residues were not observed at all.Moreover, the sputtering target of this comparative example 1 was usedto form a thin film on the film substrate as in the foregoing practicalexamples. This thin film was 420 μΩ·cm in resistivity and 88% intransparency. Besides, the work function was 5.18 eV.

Then, the sputtering target of the comparative example 1-2 has a densityof 6.85 g/cc and a bulk resistivity of 0.46 mΩ·cm. The sputtering targetof this comparative example 1-2 was used to form a thin film on theglass substrate as in the foregoing practical examples. This thin filmwas 170 μΩ·cm in resistivity and 90% in transparency. The work functionwas 4.92 eV. As for the etching characteristic, a large amount ofresidues were observed which precluded the etching. Moreover, thesputtering target of this comparative example 1-2 was used to form athin film on the film substrate as in the foregoing practical examples.This thin film was 680 μΩ·cm in resistivity and 89% in transparency.Besides, the work function was 4.88 eV.

Moreover, the sputtering target of the comparative example 1-3 had adensity of 6.90 g/cc and a bulk resistivity over MΩ·cm. The sputteringtarget of this comparative example 1-2 was used to form a thin film onthe glass substrate by the rf magnetron sputtering method as in theforegoing practical examples. This thin film was over MΩ·cm inresistivity and 89% in transparency. The work function was 5.58 eV. Asfor the etching characteristic, etching could not be done, the etchingbeing impossible. Moreover, the sputtering target of this comparativeexample 1-3 was used to form a thin film on the film substrate in thesame manner. This thin film was over MΩ·cm in resistivity and 88% intransparency. Besides, the work function was 5.55 eV.

Thus, as can be seen from the contrast between the practical examplesand the comparative examples, any of the sputtering targets of thepractical examples have a work function of 5.50 eV or greater in valuewhile maintaining a transparency of 87% or higher. Consequently, whenorganic EL devices or organic phosphorescence type light emittingdevices are fabricated by using such thin films as shown in thepractical examples for transparent electrodes thereof, it is possible toobtain devices of improved hole injection rates.

Summary of the Group of Embodiments 1

As described above, according to the aspect of the first group of thepresent invention, the inclusion of such metals as lanthanides andhafnium makes it possible to provide a transparent conductive film ofhigher work function while maintaining transparency. As a result,according to the present invention, it becomes possible to obtainorganic EL devices and organic phosphorescence type light emittingdevices of improved hole injection efficiencies.

Group of Embodiments 2 Embodiment 2-1

Initially, with reference to FIG. 3, description will be given of anembodiment 2-1 according to the organic EL device of the presentinvention. FIG. 3 is a sectional view of an organic EL device 100. Asshown in this diagram, the organic EL device 100 has the structure thatan anode layer 10, an organic luminescent layer 14, and a cathode layer16 are laminated on a substrate (not shown) in succession.

Hereinafter, description will concentrate on the anode layer 10 and theorganic luminescent layer 14 which are the characteristic parts of theembodiment 2-1. The configuration and forming method of the rest of thecomponents, such as the cathode layer 16, will be described in thebriefest form. As for parts that are not mentioned, variousconfigurations and forming methods generally known in the field oforganic EL devices may be employed.

Incidentally, in the embodiment 2-1, the anode layer 10 is made ofcompounds of group A-1 or A-2 (which will hereinafter be referred tocollectively as group A) and group B-1 or B-2 (which will hereinafter bereferred to collectively as group B) to be described below.Nevertheless, the cathode layer 16 may be made of the foregoinginorganic compounds when the work functions of the foregoing inorganiccompounds are rendered below 4.0 eV in value.

(1) Constituent Materials of the Anode Layer 10

The anode layer 10 of the present embodiment 2-1 adopts either theconstitution of containing an inorganic compound of the following groupA-1 and a compound of the group B-1 in combination or the constitutionof containing an inorganic compound of the following group A-2 and acompound of the group B-2 in combination. Note that the combinations ofinorganic compounds of the group A-1 and compounds of the group B-1 andthe combinations of inorganic compounds of the group A-2 and compoundsof the group B-2 have some overlapping compounds:

Group A-1: chalcogenides, oxynitrides, or nitrides of Si, Ge, Sn, Pb,Ga, In, Zn, Cd, and Mg;

Group A-2: chalcogenides, oxynitrides, or nitrides of Ge, Sn, Pb, Ga,In, Zn, Cd, and Mg;

Group B-1: chalcogenides, oxynitrides, or nitrides of lanthanides; and

Group B-2: chalcogenides of lanthanides.

The compounds of two types, the group A and the group B, are thuscombined because it is difficult, as described above, for either one(group A or group B) of compounds (organic compound or inorganiccompound) alone to increase the value of ionization potentialeffectively. Specifically, it is difficult to increase the ionizationpotential to values above 5.8 eV.

Consequently, the inorganic compounds of the group A-1 and the compoundsof the group B-1, or the inorganic compounds of the group A-2 and thecompounds of the group B-2, can be combined to constitute the anodelayer 10 so that the ionization potential has an extremely large valueof 5.8 eV or above. As a result, an organic EL device can be obtainedwhich has excellent durability and transparency, a low driving voltage(low specific resistance), and high luminescence intensity.

Moreover, the compounds combining the inorganic compounds of the groupA-1 and the compounds of the group B-1, or the compounds combining theinorganic compounds of the group A-2 and the compounds of the group B-2,are characterized by having excellent etching properties to acids suchas hydrochloric acid and oxalic acid. Specifically, the interfacebetween an acid-treated part and an untreated part exhibits a smoothsection, which allows clear distinction between the areas of theacid-treated part and the untreated part. Electrode layers made of suchinorganic compounds thus have electrode patterns of excellent etchingprecision, with the effect that even microelectrodes and electrodes ofcomplicated shapes are less prone to disconnection, deformation,increased resistance, and so on.

Group A Inorganic Compounds

More specifically, the inorganic compounds of group A-1 include SiOx(1≦x≦2), GeOx (1≦x≦2), SnO₂, PbO, In₂O₃, ZnO, GaO, CdO, ZnS, ZnCe, CdSe,InxZnyO (0.2≦x/(x+y)≦0.95), ZnOS, CdZnO, CdZnS, MgInO, CdInO, MgZnO,GaN, InGaN, and MgZnSSe.

Moreover, the inorganic compounds of the group A-2 specifically includethe foregoing inorganic compounds of group A-1 excluding SiOx (1≦x≦2)etc. Naturally, ZnO here means oxides of Zn, and ZnS sulfides of Zn. Inparticular, in the present embodiment, Zn and O, and Zn and S, are notalways in their respective regular compositions of 1:1 in ratio.Compounds out of the proportions are also included.

Moreover, particularly preferable materials among the inorganiccompounds of the group A-1 and the group A-2 are chalcogenides of Sn,In, and Zn or nitrides of the same. The reason for this is that thesecompounds, as partly described above, have smallest absorptioncoefficients or smallest quenching properties in particular among theinorganic compounds of the group A-1 and the group A-2, with excellenttransparency so that more amounts of light can be taken out. Of thechalcogenides of Ge, Sn, Zn, and Cd mentioned above, the oxides thereofare yet preferable in particular.

Group B Compounds

Now, the compounds of the group B-1 specifically include Ce₂O₃, CeO₂,Pr₆O₁₁, Nd₂O₃, Sm₂O₃, Eu₂O₃, Gd₂O₃, Tb₄O₇, Dy₂O₃, Ho₂O₃, Er₂O₃, Tm₂O₃,Yb₂O₃, Lu₂O₃, CeN, PrN, NdN, SmN, EuN, GdN, TbN, DyN, HoN, ErN, TmN,YbN, and LuN. They can be used alone or combinations of two or moretypes of these.

Moreover, the compounds of the group B-2 specifically include ones orcombinations of two or more types selected from the group consisting ofCe₂O₃, CeO₂, Pr₆O₁₁, Nd₂O₃, Sm₂O₃, Eu₂O₃, Gd₂O₃, Tb₄O₇, Dy₂O₃, Ho₂O₃,Er₂O₃, Tm₂O₃, Yb₂O₃, and Lu₂O₃.

Of these compounds of the group B-1 and the group B-2, oxides of Ce, Nd,Sm, Eu, Tb, and Ho, i.e., CeOx, Nd₂O₃, Sm₂O₃, Eu₂O₃, Tb₄O₇, and Ho₂O₃are yet preferable. The reason for this is also that, as partlydescribed above, the use of these inorganic compounds can increase thevalue of the ionization potential in the anode layer 10 effectively.

Content of the Group B (Group B-1 or Group B-2) Compound

Next, description will be given of the content of the group B (group B-1or group B-2 will be referred to simply as group B) compound. Thecontent of such a group B compound preferably has a value within therange of 0.5 and 30 at. % with the total amount of the anode layer 10 as100 at. %. The reason for this is that if the content of the group Bcompound falls below 0.5 at. %, the anode layer 10 deteriorates inionization potential adjustability. Specifically, it might be difficultto adjust the ionization potential into the range of 5.65 and 6.40 eV.On the other hand, when the content of the group B compound exceeds 30at. %, there might occur a conductivity drop, coloring, or atransparency (light-transmittance) drop.

Consequently, in view of better balance between the adjustability of thevalue of the ionization potential in the anode layer 10 and thetransparency etc., the content of the group B compound preferably has avalue within the range of 0.8 and 20 at. %, and yet preferably a valuewithin the range of 1 and 10 at. %, with the total amount of the anodelayer as 100 at. %.

Content of the Group A (Group A-1 or Group A-2) Compound

Incidentally, the content of the group A (group A-1 or group A-2 will bereferred to simply as group A) inorganic compound has a value that isobtained by subtracting the content of the group B compound from thetotal amount of 100 at. % when the anode layer 10 is composed of thecompounds of the group A (group A-1 or group A-2) and the group B (groupB-1 or group B-2). Thus, when the content of the group B compound in theanode layer 10 has a value within the range of 0.5 and 30 at. %, thecontent of the group A inorganic compound in the anode layer 10 is avalue within the range of 70 and 99.5 at. %.

Nevertheless, when the anode layer 10 contains any compound (thirdcomponent) other than group A and group B, the content of the group Ainorganic compound is preferably determined in consideration of thecontent of the third component.

Thickness and Structure of the Anode Layer

The anode layer 10 is not limited to any particular thickness, but ispreferably given a value, in concrete terms, within the range of 0.5 and1000 nm. The reason for this is that if the anode layer 10 has athickness below 0.5 nm, pin holes can occur to cause a leak current in along-term use. On the other hand, when the anode layer 10 has athickness above 1000 nm, the electrode transparency can fall with a dropin luminescence intensity. Consequently, in view of better balancebetween the durability and the driving voltage value etc., the anodelayer 10 preferably has a thickness within the range of 1.0 and 800 nm,and yet preferably a thickness within the range of 2.0 and 300 nm. Theanode layer 10 is not limited to any particular structure, either. Botha single-layer structure and a multilayer structure having two or morelayers are applicable. Consequently, when yet higher transparency (lighttransmittance) or yet higher conductivity is desired, a double-layerstructure may be formed through lamination on a conductive electrodelayer of higher transparency or a conductive electrode layer of higherconductivity, such as ITO and In₂O₃—ZnO.

Specific Resistance of the Anode Layer

Next, description will be given of the specific resistance of the anodelayer 10. This specific resistance is not limited to any particularvalue, but is preferably given a value below 1 Ω·cm, for example. Thereason for this is that if the specific resistance has a value of 1 Ω·cmor higher, there can occur uneven luminescence within pixels as well asan increase in the driving voltage of the organic EL devices fabricated.Consequently, in order to achieve a lower driving voltage, the specificresistance of the anode layer 10 preferably has a value of 40 mΩ·cm orsmaller, and yet preferably a value of 1 mΩ·cm or smaller. Incidentally,the value of the specific resistance of the anode layer 10 can bedetermined by measuring the surface resistance with a resistance meterof four probe method and measuring the thickness separately.

Method of Forming the Anode Layer

Next, description will be given of a method of forming the anode layer10. This forming method is not limited to any particular method. Forexample, it is possible to adopt such methods as sputtering, vapordeposition, spin coating, a casting-based sol-gel method, spraypyrolysis, and ion plating. In particular, high frequency magnetronsputtering is preferably adopted. In concrete terms, the sputtering ispreferably performed under the condition of 1×10⁻⁷ to 1×10⁻³ Pa invacuum, 0.01 to 50 nm/sec in the rate of film formation, and −50 to 300°C. in substrate temperature.

(2) Organic Luminescent Layer

Now, description will be given of the organic luminescent layer.

Constituent Material of the Organic Luminescent Layer

Organic luminescent material to be used as the constituent material ofthe organic luminescent layer preferably combines the following threefunctions:

(a) Charge injecting function: a function of enabling hole injectionfrom the anode layer or a hole injection layer and enabling electroninjection from the cathode layer or an electron injection layer underthe application of an electric field;

(b) Transporting function: a function of moving injected holes andelectrons by force of the electric field; and

(c) Luminescence function: a function of providing a field for electronsand holes to recombine, thus contributing luminescence.

Nevertheless, it is not always necessary to combine all the foregoingfunctions (a) to (c). For example, suitable organic luminescentmaterials are also found in ones that have hole injection andtransportation capabilities much superior to their electron injectionand transport capabilities. Thus, materials can be suitably used as longas they promote electron movement in the organic luminescent layer 14 toallow recombination of holes and electrons in the organic luminescentlayer 14 near the center.

Here, for the sake of improved recombinability of the organicluminescent layer 14, the organic luminescent material preferably has anelectron mobility of 1×10⁻⁷ cm²/V·s or greater. The reason for this isthat values below 1×10⁻⁷ cm²/V·s can make quick response of the organicEL device difficult and reduce the luminescence intensity. Consequently,the electron mobility of the organic luminescent material preferably hasa value within the range of 1.1×10⁻⁷ and 2×10⁻³ cm²/V·s, and yetpreferably a value within the range of 1.2×10⁻⁷ and 1.0×10⁻³ cm²/V·s.

Moreover, the organic luminescent material of the organic luminescentlayer 14 preferably has an electron mobility smaller than its holemobility in value. The reason is that if this relationship is inverse,organic luminescent materials available for the organic luminescentlayer 14 can be restricted excessively and the luminescence intensitymight drop. Meanwhile, the electron mobility of the organic luminescentmaterial is preferably rendered greater than 1/1000 of the value of thehole mobility. The reason is that too small an electric mobility canmake it difficult for holes and electrons to recombine the organicluminescent layer 14 near the center and the luminescence intensitymight drop again. Consequently, the hole mobility (μh) and electronmobility (μe) of the organic luminescent material of the organicluminescent layer 14 preferably satisfy the relationship ofμh/2>μe>μh/500, and yet preferably satisfy the relationship ofμh/3>μe>μh/100.

Moreover, in the present embodiment 2-1, the organic luminescent layer14 preferably contains aromatic ring compounds having styryl groupsexpressed by the foregoing general formulae (2-1) to (2-3). The aromaticring compounds having such styryl groups can be used to facilitatesatisfying the condition on the electron mobility and hole mobility ofthe organic luminescent material of the organic luminescent layer 14described above. Among the aromatic groups having 6 to 40 carbon atomsin the general formulae (2-1) to (2-3), the preferred 5- to 40-nucleusaryl groups include phenyl, naphthyl, anthranyl, pyrenyl, coronyl,biphenyl, terphenyl, pirrolyl, furanyl, thiophenyl, benzothiophenyl,oxadiazolyl, diphenylanthranyl, indolyl, carbazolyl, pyridyl, andbenzoquinolyl.

Besides, the preferred 5- to 40-nucleus arylene groups includephenylene, naphthylene, anthranylene, phenanthrylene, pyrenylene,coronylene, biphenylene, terphenylene, pyrrolylene, furanylene,thiophenylene, benzophenylene, oxadiazolylene, diphenylanthranylene,indolylene, carbazolylene, pyridylene, and benzoquinolylene.Incidentally, the aromatic groups having 6 to 40 carbon atoms mayfurther be substituted with substituent groups. The preferredsubstituent groups include 1- to 6-carbon alkyl groups (ethyl group,methyl group, i-propyl group, n-propyl group, s-butyl group, t-butylgroup, pentyl group, hexyl group, cyclopentyl group, cyclohexyl group,etc.), 1- to 6-carbon alkoxyl groups (ethoxy group, methoxy group,i-propoxy group, n-propoxy group, s-butoxy group, t-butoxy group,pentoxy group, hexyloxy group, cycropentoxy group, cyclohexyloxy group,etc.), 5- to 40-nucleus aryl groups, amino groups substituted with 5- to40-nucleus aryl groups, ester groups having 5- to 40-nucleus arylgroups, ester groups having 1- to 6-carbon alkyl groups, cyano group,nitro group, and halogen atom.

It is also preferable for the organic luminescent layer 14 to containfluorescent brighteners of benzothiazole type, benzimidazole type,benzoxazole type and the like, compounds of styrylbenzene type, andmetal complexes having 8-quinolinol derivatives as a ligand. Moreover,one having a host of distyrylarylene-skeleton organic luminescentmaterial, such as 4,4′-bis(2,2-diphenylvinyl)biphenyl, doped with blueto red strong fluorochomes, such as fluorochromes of cumarin type orones similar to the host, is also suitably used.

Method of Forming the Organic Luminescent Layer

Next, description will be given of a method of forming the organicluminescent layer 14. This forming method is not limited to anyparticular method. For example, it is possible to adopt such methods asvacuum deposition, spin coating, casting, LB method, and sputtering. Forexample, in the case of formation through vacuum deposition, it ispreferable to satisfy the condition of 50° C. to 450° C. in depositiontemperature, 1×10⁻⁷ to 1×10⁻³ Pa in vacuum, 0.01 to 50 nm/sec in therate of film formation, and −50° C. to 300° C. in substrate temperature.

The organic luminescent layer 14 can also be formed by dissolving abinder and an organic luminescent material in a predetermined solvent,and then making it into a thin film by spin coating or the like.Incidentally, the forming method and forming condition are preferablyselected as appropriate so that the organic luminescent layer 14 is amolecular deposition film, which is a thin film formed throughdeposition from a material compound in a vapor phase or a film formedthrough solidification from a material compound in a solution or liquidphase. Typically, this molecular deposition film can be fullydistinguished from a thin film formed by LB method (molecularaccumulation film) based on differences in cohesion structure andhigh-order structure as well as resulting functional differences.

Thickness of the Organic Luminescent Layer

The organic luminescent layer 14 is not limited to any particularthickness, but may select an appropriate thickness as needed dependingon the circumstances. In reality, values within the range of 5 nm and 5μm are often preferable. The reason for this is that if the thickness ofthe organic luminescent layer falls below 5 nm, the luminescenceintensity and the durability might drop. On the other hand, when thethickness of the organic luminescent layer 14 exceeds 5 μm, the value ofthe voltage to be applied often becomes higher. Consequently, in view ofbetter balance with the luminescence intensity, the value of the appliedvoltage, etc., the organic luminescent layer 14 preferably has athickness within the range of 10 nm and 3 μm, and yet preferably athickness within the range of 20 nm and 1 μm.

(3) Cathode Layer

The cathode layer 16 is preferably made of metals, alloys, orelectroconductive compounds having a small work function (for example,below 4.0 eV), or mixtures of these. Specifically, one of magnesium,aluminum, indium, lithium, sodium, cesium, silver, and the like may beused alone, or two or more types thereof in combination. The cathodelayer 16 is not limited to any particular thickness, either, whereas itis preferably given a value within the range of 10 and 1000 nm, and yetpreferably a value within the range of 10 and 200 nm.

(4) Miscellaneous

Although not shown in FIG. 3, it is also preferable that a sealing layerfor preventing moisture and oxygen from getting into the organic ELdevice 100 is arranged so as to cover the entire organic EL device 100.Preferred materials of the sealing layer include: copolymers obtained bycopolymerizing tetrafluoroethylene and monomer mixtures including atleast one type of comonomer; fluorine-containing copolymers having aring structure in their copolymer main chain; and copolymers ofpolyethylene, polypropylene, polymethylmethacrylate, polyimide,polyuria, polytetrafluoroethylene, polychlorotrifluoroethylene,polydichlorofluoroethylene, or chrolotrifluoroethylene withdichlorodifluoroethylene.

The preferred materials of the sealing layer also include:water-absorbing substances having an absorptivity of 1% or higher;moisture-proof substances having an absorptivity of 0.1% or lower;metals such as In, Sn, Pb, Au, Cu, Ag, Al, Ti, and Ni; metal oxides suchas MgO, SiO, SiO₂2, GeO, NiO, CaO, BaO, Fe₂O, Y₂O₃, and TiO₂; metalfluorides such as MgF₂, LiF, AlF₃, and CaF₂; liquid fluorocarbons suchas perfluoroalkane, perfluoroamine, and perfluoropolyether; andcompositions of those liquid fluorocarbons in which absorbents forabsorbing moisture and oxygen are dispersed.

To form the sealing layer, it is possible to employ vacuum deposition,spin coating, sputtering, casting, MBE (molecular beam epitaxy), clusterion beam deposition, ion plating, plasma polymerization (high frequencyexcitation ion plating), reactive sputtering, plasma CVD, laser CVD,thermal CVD, gas-source CVD, and the like as appropriate.

Embodiment 2-2

Next, with reference to FIG. 4, description will be given of anembodiment 2-2 of this invention. FIG. 4 is a sectional view of anorganic EL device 102 according to the embodiment 2-2, showing thedevice having the structure that an anode layer 10, an inorganic thinfilm layer 12, an organic luminescent layer 14, and a cathode layer 16are laminated on a substrate (not shown) in succession. When theinorganic thin film layer 12 is provided thus, injected holes can betransported effectively. Consequently, the provision of the inorganicthin film layer 12 allows low-voltage driving and improves thedurability of the organic EL device 102.

Incidentally, the organic EL device 102 of the embodiment 2-2 ischaracterized in that the inorganic thin film layer 12 is interposedbetween the anode layer 10 and the organic luminescent layer 14. Inother respects, it has the same structure as that of the organic ELdevice 100 of the embodiment 2-1.

Hence, the following description will deal mainly with the inorganicthin film layer 12 which is the characteristic part of the embodiment2-2. See the description of the embodiment 2-1 for the rest of thecomponents, such as the cathode layer 16, since they have the sameconfiguration as in the first embodiment.

Now, the inorganic compounds available to constitute the inorganic thinfilm layer 12 include combinations of the compounds of the group A(group A-1 or group A-2) and the group B (group B-1 or group B-2) whichconstitute the anode layer 10 described above. Thus, as in the anodelayer 10, the content of such a group B compound is preferably given avalue within the range of 0.5 and 50 at. %, yet preferably a valuewithin the range of 1.0 and 40 at. %, and even more preferably a valuewithin the range of 5.0 and 30 at. % with the total amount of theinorganic thin film layer as 100 at. %. It is also preferable that thethickness and forming method thereof are the same as those of the anodelayer 10.

Nevertheless, when the inorganic thin film layer 12 is arranged betweenthe anode layer 10 and the organic luminescent layer 14, the anode layer10 and the inorganic thin film layer 14 must be given differentcompositions. Specifically, the anode layer 10 is preferably made of thecompounds of group A (group A-1 or group A-2)/group B (group B-1 orgroup B-2)=70 to 90 at. %/0.5 to 10 at. % while the inorganic thin filmlayer 12 the inorganic compounds of group A (group A-1 or groupA-2)/group B (group B-1 or group B-2)=50 to below 90 at. %/above 10 at.% to 50 at. %. The reason for this is that if the amount of the group B(group B-1 or group B-2) compound falls outside this range, there canoccur a drop in transparency and an increase in specific resistancewhich are unfavorable for electrodes.

Embodiment 2-3

Next, with reference to FIG. 5, description will be given of anembodiment 2-3 of this invention. FIG. 5 is a sectional view of anorganic EL device 104 according to the embodiment 2-3, showing thedevice having the structure that an anode layer 10, an inorganic thinfilm layer 12, a hole transporting layer 13, an organic luminescentlayer 14, and a cathode layer 16 are laminated on a substrate (notshown) in succession.

In the present embodiment 2-3, the provision of the hole transportinglayer 13 in addition to the embodiments 2-1 and 2-2 allows efficienttransportation of injected holes. Consequently, the provision of thehole transporting layer 13 allows low-voltage driving and improves thedurability of the organic EL device 104.

Incidentally, the organic EL device 104 of the present embodiment 2-3has the same structure as that of the organic EL device 102 of theembodiment 2-2 except that the hole transporting layer 13 is interposedbetween the inorganic thin film layer 12 and the organic luminescentlayer 14. Hence, the following description will deal mainly with thehole transporting layer 13 which is the characteristic part of theembodiment 2-3. See the description of the foregoing embodiments 2-1 and2-2 for the rest of the components, such as the cathode layer 16, sincethey may be configured the same as in the embodiments 2-1 and 2-2.

(1) Constituent Material of the Hole Transporting Layer 13

The hole transporting layer 13 is preferably made of an organic compoundor inorganic compound. Such organic materials include, for example,phthalocyanine compounds, diamine compounds, diamine-containingoligomers, and thiophene-containing oligomers. Preferred materials ofthe inorganic compound include, for example, amorphous silicon (α-Si),α-SiC, microcrystalline silicon (μC—Si), μC—SiC, II-VI family compounds,III-V family compounds, noncrystalline carbon, crystalline carbon, anddiamond. Among other types of the inorganic material are oxides,fluorides, and nitrides. To be more specific, Al₂O₃, SiO, SiOx (1≦x≦2),GaN, InN, GaInN, GeOx (1≦x≦2), LiF, SrO, CaO, BaO, MgF₂, CaF₂, UgF₂,SiNx (1≦x≦4/3), and the like can be used alone, or two or more typesthereof in combination. Besides, the constituent material is preferablyselected so that the hole mobility has a value of 1×10⁶ cm²/V·s orgreater (applied voltage of 1×10⁴ to 1×10⁶ V/cm), and the ionizationpotential has a value of 5.5 eV or lower.

(2) Structure and Forming Method of the Hole Transporting Layer 13

The hole transporting layer 13 is not limited to the single-layerstructure, but may have a double-layer structure or a triple-layerstructure, for example. The hole transporting layer 13 is not limited toany particular thickness, either, whereas a value within the range of0.5 nm and 5 μm is preferable. The hole transporting layer 13 is notlimited to any particular forming method, either. A variety of methodscan be adopted. In reality, however, it is preferable to adopt the samemethod as the method of forming the hole injection layer.

Embodiment 2-4

Next, with reference to FIG. 6, description will be given of anembodiment 2-4 of this invention. FIG. 6 is a sectional view of anorganic EL device 106 according to the embodiment 2-4, showing thedevice having the structure that an anode layer 10, an inorganic thinfilm layer 12, a hole transporting layer 13, an organic luminescentlayer 14, an electron injection layer 15, and a cathode layer 16 arelaminated on a substrate (not shown) in succession. As above, in theembodiment of the present section 4, the provision of the electroninjection layer 15 allows the function of injecting electronseffectively. The provision of the electron injection layer 15 thusfacilitates moving electrons to the organic luminescent layer 14, withan improvement to the responsivity of the organic EL device 106.

Incidentally, the organic EL device 106 of the embodiment 2-4 ischaracterized in that the electron injection layer 15 is interposedbetween the organic luminescent layer 14 and the cathode layer 16.Except this, the organic EL device 106 of the embodiment 2-4 has thesame structure as that of the organic EL device 104 of the embodiment2-3. Hence, the following description will deal mainly with the electroninjection layer 15 which is the characteristic part of the embodiment2-4. The rest of the components may adopt the same configurations as inthe embodiments 2-1 to 2-3 described above, or typical publicly-knownconfigurations in the field of organic EL devices.

(1) Constituent Material of the Electron Injection Layer

The electron layer 15 is preferably made of an organic compound orinorganic compound. In particular, organic compounds can be used toconstitute an organic EL device that has excellent electroninjectability from the cathode as well as an excellent durability. Here,preferred organic compounds include 8-hydroxyquinoline and oxadiazol,and derivatives thereof such as metal chelate oxinoid compoundscontaining 8-hydroxyquinoline.

When the electron injection layer 15 is made of an inorganic compound,this inorganic compound preferably uses an insulator or semiconductor.The electron injection layer 15, when made of an insulator orsemiconductor, can effectively avoid current leak and improve electroninjectability. For such an insulator, it is preferable to use at leastone metal compound selected from the group consisting of alkaline metalchalcogenides (oxides, sulfides, selenides, tellurides), alkaline earthmetal chalcogenides, halides of alkaline metals, and halides of alkalineearth metals. When the electron injection layer 15 is made of thesealkaline metal chalcogenides or the like, the electron injectability ispreferably improved further.

Specifically, the preferred alkaline metal chalcogenides include Li₂O,LiO, Na₂S, Na₂Se, and NaO, for example. The preferred alkaline earthmetal chalcogenides include CaO, BaO, SrO, BeO, BaS, and CaSe, forexample. In addition, the preferred halides of alkaline metals includeLiF, NaF, KF, LiCl, KCl, and NaCl, for example. The preferred halides ofalkaline earth metals include, for example, fluorides such as CaF₂,BaF₂, SrF₂, MgF₂, and BeF₂, and halides other than fluorides.

Now, when the electron injection layer 15 is made of a semiconductor,preferred semiconductors include oxides, nitrides, or nitric oxidescontaining at least one element out of Ba, Ca, Sr, Yb, Al, Ga, In, Li,Na, Cd, Mg, Si, Ta, Sb, and Zn. They can be used alone, or two or moretypes thereof in combination. Moreover, it is preferable that theinorganic compound for constituting the electron injection layer 15 is amicrocrystalline or noncrystalline insulative thin film. The electroninjection layer 15, when made of these insulative thin films, can form amore homogenous thin film to reduce defective pixels such as dark spots.Incidentally, such inorganic compounds include the alkaline metalchalcogenides, the alkaline earth metal chalcogenides, the halides ofalkaline metals, and the halides of alkaline earth metals describedabove.

(2) Electron Affinity

Now, the electron injection layer 15 according to the embodiment 2-4preferably has an electron affinity within the range of 1.8 and 3.6 eV.When the electron affinity falls below 1.8 eV in value, the electroninjectability drops with the tendency toward higher driving voltage andlower luminescent efficiency. When the electron affinity exceeds 3.6 eVin value, on the other hand, the probability of occurrence of complexeshaving lower luminescent efficiency increases while it becomes possibleto suppress the occurrence of blocking junction effectively. Thus, theelectron affinity of the electron injection layer is preferably given avalue within the range, of 1.9 and 3.0 eV, and yet more preferably avalue within the range of 2.0 and 2.5 eV. Moreover, the difference inelectron affinity between the electron injection layer 15 and theorganic luminescent layer 14 preferably has a value of 1.2 eV orsmaller, and yet preferably a value of 0.5 eV or smaller. The smallerthis difference in electron affinity is, the easier the electioninjection from the electron injection layer 15 to the organicluminescent layer 14 becomes. This makes it possible to constitute theorganic EL device 106 of improved responsivity.

(3) Energy Gap

The electron injection layer 15 according to the embodiment 2-4preferably has an energy gap (band gap energy) of 2.7 eV or greater, andyet preferably a value of 3.0 eV or greater. When the energy gap is thusset at or above a predetermined value, e.g., a value as great as orabove 2.7 eV, it is possible to reduce the chance that holes reach theelectron injection layer 15 beyond the organic luminescent layer 14.This can improve the efficiency of the recombination between holes andelectrons, enhancing the luminescence intensity of the organic EL device106. It is also possible to prevent the electron injection layer 15itself from emitting light.

(4) Structure

Now, description will be given of the structure of the electroninjection layer 15 that is made of an inorganic compound. This electroninjection layer 15 is not limited to any particular structure, but mayhave a single-layer structure, double-layer structure, or triple-layerstructure, for example. Moreover, the electron injection layer 15 is notlimited to any particular thickness, either. Various thicknesses may beemployed depending on the circumstances. In reality, values within therange of, e.g., 0.1 nm and 1000 nm are preferable. The reason for thisis that when the electron injection layer 15 made of an inorganiccompound falls below 0.1 nm in thickness, there may occur a drop inelectron injectability or a drop in mechanical strength. On the otherhand, when the electron injection layer 15 made of an inorganic compoundexceeds 1000 nm in thickness, it becomes high in resistance, possiblydeteriorating the responsivity of the organic EL device 106, i.e.,making quick response difficult, or requiring time for film formation.Consequently, the electron injection layer 15 made of an inorganiccompound preferably has a thickness within the range of 0.5 and 100 nm,and yet more preferably a thickness within the range of 1 and 50 nm.

(5) Forming Method

Next, description will be given of a method of forming the electroninjection layer 15. The electron injection layer 15 is not limited toany particular forming method as long as it can be formed as a thin filmlayer of uniform thickness. Various types of methods, such as vacuumdeposition, spin coating, casting, LB method, and sputtering, areapplicable.

Embodiment 2-5

Now, description will be given of an embodiment 2-5 of the presentinvention. In the embodiment 2-5, a plurality of inorganic compounds canbe used to achieve an anode layer 16 of excellent etching property andtransparency in which the constituent materials are in uniformcomposition ratios. As a result, a fabrication method is provided bywhich an organic EL device of low driving voltage, excellentluminescence intensity, and excellent durability can be obtained withefficiency. That is, a first characteristic of the embodiment 2-5 liesin that the anode layer 16 is formed by using certain targets andsputtering method. Moreover, in the embodiment 2-5, for example, aplurality of organic luminescent materials can be used to achieve anorganic luminescent layer 14 in which the constituent materials are inuniform composition ratios. As a result, a fabrication method isprovided by which an organic EL device of low driving voltage, highluminescence intensity, and excellent durability can be obtained withefficiency. That is, a second characteristic of the embodiment 2-5 liesin that the organic luminescent layer 14 is made of a plurality oforganic compounds by using a certain vacuum deposition method.

In order to obtain the organic EL device having the property that itsconstituent materials are in uniform composition ratios, at least theanode layer 10 and the organic luminescent layer 14 are preferablyformed under a consistent identical vacuum condition without beingexposed to the air. A third characteristic of the embodiment 2-5 lies inthe sharing of a vacuum chamber for exercising sputtering and a vacuumchamber for exercising vacuum deposition. The reason is to obtain anorganic EL device having the property that the constituent materials arein uniform composition ratios. Then, in the embodiment 2-5, a singlevacuum chamber is provided not only with a heating unit and substrateholding means necessary for exercising sputtering but also with aheating unit, evaporation sources, and the like for exercising vacuumdeposition. This allows the sharing of the vacuum tube for exercisingsputtering and the vacuum chamber for exercising vacuum deposition.Incidentally, as a modified example of the embodiment 2-5, it ispossible to employ the configuration that the vacuum chamber forsputtering and the vacuum chamber for vacuum deposition are arrangedseparately and are connected to each other in advance. According to sucha modification, a substrate given vacuum deposition can be thentransported into the vacuum chamber for sputtering by a predeterminedtransportation unit, with the same result as in the case of sharing thevacuum chamber. For ease of understanding, the organic EL device to bedescribed in the present embodiment 2-5 shall have the sameconfiguration as that of the embodiment 2-5.

According to the fabrication method employed in the embodiment 2-5, thelayers shown below were formed by the respective correspondingfabrication methods:

Anode layer 10: high frequency magnetron sputtering;

Inorganic thin film layer 12: high frequency magnetron sputtering;

Hole transporting layer 13: vacuum deposition;

Organic luminescent layer 14: vacuum deposition;

Electron injection layer 15: vacuum deposition; and

Cathode layer 16: vacuum deposition.

(1) Formation of the Anode Layer and the Inorganic Thin Film Layer

In forming the anode layer 10 and the inorganic thin film layer 12 byhigh frequency magnetron sputtering, it is preferable to use a targetthat is made of compounds of the group A (group A-1 or group A-2) andthe group B (group B-1 or group B-2). Specifically, the target mustcontain at least the group A (group A-1 or group A-2) and the group B(group B-1 or group B-2) in predetermined proportions. Moreover, thetarget (1 μm or less in average particle diameter), or raw material, ispreferably obtained by being mixed uniformly by using a solution method(coprecipitation method) (concentration: 0.01 to 10 mol/liter; solvent:polyhydric alcohol or the like; precipitating agent: potassium hydroxideor the like) and a physical mixing method (mill: ball mill, bead mill,or the like; mixing period: 1 to 200 hours) and then sintered (attemperatures of 1200° C. to 1500° C., for a period of 10 to 72 hours orpreferably 24 to 48 hours), followed by molding (press molding, HIPmolding, or the like). Here, the rate of temperature rise during themolding preferably falls within the range of 1 and 50° C./minute invalue. The target obtained by these methods is characterized by havingthe property that its constituent materials are in uniform compositionratios. Incidentally, since the composition ratios and the like can beadjusted by the sputtering condition alone, it is also preferable thatthe compounds of the group A (group A-1 or group A-2) and the group B(group B-1 or group B-2) are sputtered separately.

The sputtering condition is not limited to any particular one, whereasit is preferable to employ the condition of: in argon or other inertgas; 0.3 to 4 W in plasma output per a 1-cm² surface area of the target;1×10⁻⁷ to 1×10⁻³ Pa in vacuum; 0.01 to 50 nm/sec in the rate of filmformation; 5 to 120 minutes in the period of film formation; and −50° C.to 300° C. in substrate temperature. The reason is that such asputtering condition is cost-effective and capable of forming a denseanode layer 16 and inorganic thin film layer 12 having uniform filmthicknesses.

(2) Formation of the Organic Luminescent Layer 14

With reference to FIGS. 7 and 8, description will be given of the methodof forming the organic luminescent layer 14 by evaporating differentevaporation materials at the same time. Initially, the rotation axis213A for a substrate 203 to make self rotation about is set on thatsubstrate 203 by using a vacuum evaporator 201. Next, evaporationsources 212A to 212F are arranged at positions each away from therotation axis 213A of the substrate 203, and the substrate 203 isrotated about itself. At the same time, various evaporation materialsare evaporated simultaneously from the plurality of evaporation sources212A to 212F which are arranged opposite to the substrate 203, therebyexercising deposition. The organic luminescent layer 14 can be obtainedin this way.

Here, the vacuum evaporator 201 shown in FIGS. 7 and 8 comprises: avacuum chamber 210; a substrate holder 211 for fixing the substrate 203to the inner top part of this vacuum chamber 210; and the plurality(six) of evaporation sources 212A to 212F to be filled with evaporationmaterials, opposed to and arranged below this substrate holder 211. Thisvacuum chamber 210 is configured capable of maintaining its interior ina predetermined depressurized state by using exhaust means (not shown).Incidentally, while six evaporation sources are shown in the diagram,the number of evaporation sources is not limited thereto but may be fiveor less, or seven or more.

Now, the substrate holder 211 has a holding part 212 for holding theperiphery of the substrate 203, and is configured to hold the substrate203 horizontally in the vacuum chamber 210. A rotating shaft part 213for making the substrate 203 rotate (about itself) is erected verticallyat the center of the top surface of this substrate holder 211. Thisrotating shaft portion 213 is connected with a motor 214, rotating andagitating means. By the rotational operation of the motor 214, thesubstrate 203 held by the substrate holder 211 makes self rotation aboutthe rotating shaft portion 213, along with the substrate holder 211.That is, the vertical rotation axis 213A is established at the center ofthe substrate 203 by means of the rotating shaft portion 213.

Next, concrete description will be given of the method of forming theorganic luminescent layer 12 on the substrate 203 out of two types oforganic luminescent materials (host material and dopant material) byusing the vacuum evaporator 201 configured thus. Initially, thesubstrate 203 of flat square shape as shown in FIG. 7 is prepared. Thissubstrate 203 is locked to the holding part 212 of the substrate holder211 in a horizontal state. In this respect, the substrate 203 shown inFIG. 7 being held in a horizontal state means that the substrate 203 islocked to the holding part 212 of the substrate holder 211 in ahorizontal state.

Here, in forming the organic luminescent layer 12, the two evaporationsources 212B and 212C adjoining on an imaginary circle 221 are filledwith the host material and the dopant material, respectively. After thefilling, the vacuum chamber 210 is depressurized inside by the exhaustmeans to a predetermined vacuum such as 1.0×10⁻⁴ Torr. Then, theevaporation sources 212B and 212C are heated so that the host materialand the dopant material evaporate from the respective evaporationsources 212B and 212C simultaneously. In the meantime, the motor 214 isrotated for agitation, whereby the substrate 203 is rotated at apredetermined speed, such as 1 to 100 rpm, about the rotation axis 213A.In this way, the substrate 203 makes self rotation while the hostmaterial and the dopant material are co-evaporated to form the organicluminescent layer 12. Here, as shown in FIG. 8, the evaporation sources212B and 212C are arranged at positions off the rotation axis 213A ofthe substrate 203 by a predetermined distance M in horizontaldirections. Thus, the rotation of the substrate 203 can change theangles of incident of the evaporation materials, such as the hostmaterial and the dopant material, on the substrate 203 regularly. Thisallows the evaporation materials to adhere to the substrate 203uniformly, so that a thin film layer having evaporation materials ofuniform composition ratios can be surely formed within the film surfaceof the electrode injection layer 15. For example, it is possible to forma thin film layer having concentration variations of ±10% (on a molebasis). Moreover, when the evaporation is performed thus, no revolutionis required of the substrate 203. This eliminates the need for intendedspace and equipment, allowing economic film formation in a minimumspace. Here, the revolution of the substrate 203 refers to rotationabout any rotating axis other than that of the substrate. It requiresspace wider than in the case of self rotation.

Now, in exercising the simultaneous evaporation, the substrate 203 isnot limited to any particular shape. Take, for example, the case shownin FIG. 7 where the substrate 203 has the shape of a short plate and allthe sides of the substrate 203 are identical in length. Here, theplurality of evaporation sources 212A to 212F are arranged along thecircumference of the imaginary circle 221 around the rotation axis 213 aof this substrate 203. The short-plate shape preferably satisfiesM>(½)×L, where M is the radius of the imaginary circle 221 and L is thelength of a side of the substrate 203. On the other hand, when the sidesof the substrate 203 are not identical but different in length, L shallbe the length of the longest side. In such configurations, the angles atwhich evaporation materials are incident on the substrate 203 from theplurality of evaporation sources 212A to 212F can be rendered identical,so that the composition ratios of the evaporation materials can becontrolled more easily. Besides, due to such configurations, theevaporation materials are evaporated at a certain angle of incidence onthe substrate 203. The absence of vertical incidence can further improvethe uniformity of the composition ratios within the film surface.

Moreover, in exercising the fabrication method of the embodiment 2-5, asshown in FIG. 7, the plurality of evaporation sources 212A to 212F arepreferably arranged on the circumference of the imaginary circle 221around the rotation axis 213A of the substrate 203, the individualevaporation sources 212A to 212F being arranged at angles of 360°/nabout the center of the imaginary circle 221, where n is the number ofevaporation sources 212A to 212F to be arranged. For example, when sixevaporation sources 212 are to be arranged, they are suitably arrangedat angles of 60° about the center of the imaginary circle 221. In sucharrangement, the plurality of evaporation materials can be formed inlayers successively on each portion of the substrate 203. It istherefore possible to form a thin film layer whose composition ratiosvary regularly in the direction of the film thickness.

Next, description will be given in more detail of the compositionuniformity of the organic luminescent layer 14 that is formed by thesimultaneous evaporation method described above. By way of example, Alqwas used as the host material and Cs as the dopant. The substrate 203shown in FIG. 9 was rotated at 5 rpm while a thin film layer having athickness of approximately 1000 angstroms (setting) was simultaneouslydeposited under the following condition:

Deposition rate of Alq: 0.1 to 0.3 nm/s;

Deposition rate of Cs: 0.1 to 0.3 nm/s; and

Thickness of Alq/Cs: 1000 angstroms (setting).

Incidentally, the chemical structural formula of Alq is shown in FIG.19.

Next, the thin film layer obtained was measured for thicknesses atmeasuring points (4A to 4M) on the glass substrate 203 shown in FIG. 9by using a contact type film thickness meter. It was also measured forCs/Al (Al in Alq) composition ratios (atomic ratios) by using an X-rayphotoelectron spectroscope (XPS). Incidentally, the measuring points (4Ato 4M) on the glass substrate 203 shown in FIG. 9 are arbitrary corners(13 points) of 16 equal sections having a square shape with each side of50 mm in length P, into which the surface of the substrate 203 isdivided in advance. Table 2-1 shows the results obtained.

TABLE 2-1 Measuring point Thickness (A) Cs/Al 4A 1053 1.0 4B 1035 1.0 4C1047 1.0 4D 1088 1.1 4E 1091 1.0 4F 1093 1.1 4G 1082 1.1 4H 1075 1.0 4I1082 1.1 4J 1065 1.1 4K 1010 1.0 4L 1008 1.0 4M 1025 1.0

Meanwhile, a thin film layer having a thickness of approximately 1000angstroms (setting) was formed under the same evaporation condition asin the foregoing simultaneous evaporation method except that the glasssubstrate 203 was not rotated. The thin film layer obtained was measuredfor thicknesses and Cs/Al composition ratios (atomic ratios) at themeasuring points (4A to 4M). Table 2-2 shows the results.

TABLE 2-2 Measuring point Thickness (A) Cs/Al 4A 895 0.6 4B 941 1.1 4C884 1.1 4D 911 0.7 4E 922 1.1 4F 1022 0.8 4G 919 1.2 4H 1015 1.3 4I 10670.7 4J 908 1.2 4K 895 0.5 4L 920 1.0 4M 950 1.1

As is evident from these results, it was confirmed that according to thesimultaneous evaporation method described above, the thin film layer wasobtained with extremely uniform film thicknesses within the range of1008 and 1093 angstroms and extremely uniform Cs/Al composition ratios(atomic ratios) within the range of 1.0 and 1.10 over the measuringpoints (4A to 4M) on the substrate 203. On the other hand, in the caseof using the fabrication method different from the foregoingsimultaneous evaporation method, it was confirmed that the measuringpoints (4A to 4M) on the substrate 203 showed film thicknesses in therange of 884 and 1067 angstroms and Cs/Al composition ratios in therange of 0.6 and 1.3.

PRACTICAL EXAMPLES Practical Example 2-1 (1) Preparation for Fabricationof an Organic EL Device (Fabrication of a Target)

Powders of indium oxide and cerium oxide (no greater than 1 μm inaverage particle diameter) were accommodated in a wet ball millcontainer so that the mole ratio Ce/(In+Ce) was 0.05, and then mixed andground for 72 hours. Next, the resulting ground article was granulated,followed by press molding to dimensions of 4 inches in diameter and 5 mmin thickness. The resultant was accommodated in a baking furnace, andthen heated and baked at a temperature of 1400° C. for 36 hours tofabricate a target 2-1 for the anode layer 10.

(2) Formation of the Anode Layer 10

Then, a transparent glass substrate of 1.1 mm in thickness, 25 mm inwidth, and 75 mm in length and the obtained target 2-1 were placed inthe common vacuum chamber of the high frequency sputtering system andthe vacuum evaporator. The high frequency sputtering system was operatedto form a transparent electrode film of 75 nm in thickness as the anodelayer 10, thereby obtaining a substrate. Here, a mixed gas of argon gasand oxygen gas was filled in a state depressurized down to 3×10⁻¹ Pa invacuum. In that atmosphere, the sputtering was performed under thecondition of: an ultimate vacuum of 5×10⁻⁴ Pa; a substrate temperatureof 25° C.; an input voltage of 100 W; and a film forming time of 14minutes. Hereinafter, this glass substrate and the anode layer 10 willbe referred to collectively as a substrate. Subsequently, this substratewas subjected to ultrasonic cleaning in isopropyl alcohol, and thendried in a N₂ (nitrogen gas) atmosphere before 10-minute cleaning byusing UV (ultraviolet rays) and ozone. In this state, the anode layer 10of the substrate was measured for the value of ionization potential byusing AC-1 (from Riken Keiki Co., Ltd.) and found to be 6.20 eV.Moreover, the substrate provided with the anode layer 10 was measuredfor light transmittance (wavelength of 550 nm) and found to be 89%.

(3) Treatment in Vacuum Evaporator

The substrate was loaded on the substrate holder of the vacuum chamber.Then, the vacuum chamber was depressurized inside to a vacuum of 1×10⁻⁶Torr or lower before the hole transporting layer 13, the organicluminescent layer 14, the electron injection layer 15, and the cathodelayer 16 were laminated in succession on the anode layer 10 and theinorganic thin film layer 12 of the substrate to obtain an organic ELdevice. Here, in the period from the formation of the organicluminescent layer 14 to the formation of the cathode layer 16, thevacuum was not broken even once so that the same vacuum condition wasmaintained.

Initially, as hole transporting material, TBDB mentioned above wasvacuum-evaporated to 60 nm. Next, as the luminescent layer, DPVDPAN andD1 were co-evaporated to 40 nm in the vacuum. Here, the deposition rateof the DPVDPAN was 40 nm/s and the deposition rate of D1 was 1 nm/s.

Incidentally, the chemical structural formula of TBDB is shown in FIG.19. The chemical structural formula of DPVDPAN is also shown in FIG. 19.The chemical structural formula of D1 is also shown in FIG. 19.

Then, as the electron injection layer, Alq was vacuum-evaporated to 20nm.

Finally, Al and Li were vacuum-evaporated to form the cathode layer 16on the electron injection layer 15, fabricating the organic EL device.Here, the deposition rate of Al was 1 nm/s, and the deposition rate ofLi was 0.01 nm/s. The thickness of the Al/Li film was 200 nm.

(4) Evaluation on the Organic EL Device

A direct-current voltage of 4.8 V was applied to across electrodes withthe cathode layer 16 of the obtained organic EL device as the negative(−) electrode and the anode layer 10 as the positive (+) electrode.Here, the current density was 2.0 mA/cm² and the luminescence intensitywas 164 nit (cd/m²). The luminescent color was confirmed to be blue.Furthermore, for the sake of durability evaluation, constant-currentdriving was conducted at 10 mA/cm². No particular leak current was foundeven after a lapse of 1000 hours or more.

TABLE 2-3 Practical Practical Practical Practical embodiment embodimentembodiment embodiment 2-1 2-2 2-3 2-4 Material of In oxide/ In oxide/ Inoxide/ In oxide/ anode layer Ce oxide Sn oxide/ Sn oxide/ Sn oxide/ Znoxide/ Zn oxide/ Zn oxide/ Nd oxide/ Sm oxide/ Eu oxide/ IP (eV) 6.205.85 5.95 5.80 Thickness (nm) 75 75 75 75 Light 89 89 88 88transmittance (%) * Hole TBDB TBDB TBDB TBDB transporting materialThickness (nm) 60 60 60 60 Material of DPVDPAN DPVDPAN DPVDPAN DPVDPANluminescent layer Thickness (nm) 40 40 40 40 Material of Alq Alq Alq Alqelectron injection layer Thickness (nm) 20 20 20 20 Material of Al/LiAl/Li Al/Li Al/Li cathode layer Thickness (nm) 200 200 200 200 Voltage(V) 4.8 5.3 5.0 5.1 Luminescence 164 158 168 165 intensity (cd/m²) Halflife 1000 hours 1000 hours 1000 hours 1000 hours or more or more or moreor more * Grass reference

TABLE 2-4 Practical Practical Practical Comparative embodimentembodiment embodiment example 2-5 2-6 2-7 2-1 Material of In oxide/ Inoxide/ In oxide/ In oxide/ anode layer Sn oxide/ Sn oxide/ Sn oxide/ Snoxide/ Zn oxide/ Zn oxide/ Zn oxide/ Zn oxide/ Tb oxide/ Ho oxide/ Smoxide/ IP (eV) 5.84 5.82 5.98 5.23 Thickness (nm) 75 75 75 75 Light 8888 89 89 transmittance (%) * Hole TBDB TBDB TBDB TBDB transportingmaterial Thickness (nm) 60 60 60 60 Material of DPVDPAN DPVDPAN/DPVDPAN/ DPVDPAN/ luminescent D1 D1 D1 D1 layer Thickness (nm) 40 40 4040 Material of Alq Alq Alq Alq electron injection layer Thickness (nm)20 20 20 20 Material of Al/Li Al/Li Al/Li Al/Li cathode layer Thickness(nm) 200 200 200 200 Voltage (V) 5.1 5.1 4.9 6.0 Luminescence 165 166164 166 intensity (cd/m²) Half life 1000 hours 1000 hours 1000 hours1000 hours or more or more or more or more * Grass reference

Practical Example 2-2

Instead of the target 2-1 of the practical example 2-1, a target 2-3made of indium oxide, tin oxide, zinc oxide, and neodymium oxide wasused with indium of 0.8 in the mole ratio (In/(In+Sn+Zn)), tin of 0.1 inthe mole ratio (Sn/(In+Sn+Zn)), and zinc of 0.1 in the mole ratio(Zn/(In+Sn+Zn)). An organic EL device was fabricated with the rest ofthe fabrication condition the same as in the practical example 2-1.Incidentally, the anode layer 10 had an ionization potential of 5.85 eV.A direct-current voltage of 5.3 V was applied to across the electrodesof the obtained organic EL device as in the practical example 1, withthe result that the current density was 2.0 mA/cm² in value and theluminescence intensity was 158 nit. The luminescent color was confirmedto be blue.

Practical Example 2-3

Instead of the target 2-1 of the practical example 2-1, a target 2-4made of indium oxide, tin oxide, zinc oxide, and samarium oxide was usedwith indium of 0.8 in the mole ratio (In/(In+Sn+Zn)), tin of 0.1 in themole ratio (Sn/(In+Sn+Zn)), zinc of 0.1 in the mole ratio(Zn/(In+Sn+Zn)), and samarium of 0.04 in the mole ratio with respect tothe total metal (Sm/(In+Sn+Zn+Sm)). An organic EL device was fabricatedwith the rest of the fabrication condition the same as in the practicalexample 1. Incidentally, the anode layer 10 had an ionization potentialof 5.95 eV. A direct-current voltage of 5.0 V was applied to across theelectrodes of the obtained organic EL device as in the practical example1, with the result that the current density was 2.0 mA/cm² in value andthe luminescence intensity was 168 nit. The luminescent color wasconfirmed to be blue.

Practical Example 2-4

Instead of the target 2-1 of the practical example 2-1, a target 2-5made of indium oxide, tin oxide, zinc oxide, and europium oxide was usedwith indium of 0.8 in the mole ratio (In/(In+Sn+Zn)), tin of 0.1 in themole ratio (Sn/(In+Sn+Zn)), zinc of 0.1 in the mole ratio(Zn/(In+Sn+Zn)), and europium of 0.04 in the mole ratio with respect tothe total metal (Eu/(In+Sn+Zn+Eu)). An organic EL device was fabricatedwith the rest of the fabrication condition the same as in the practicalexample 2-1. Incidentally, the anode layer 10 had an ionizationpotential of 5.80 eV. A direct-current voltage of 5.1 V was applied toacross the electrodes of the obtained organic EL device as in thepractical example 2-1, with the result that the current density was 2.0mA/cm² in value and the luminescence intensity was 165 nit. Theluminescent color was confirmed to be blue.

Practical Example 2-5

Instead of the target 2-1 of the practical example 2-1, a target 2-6made of indium oxide, tin oxide, zinc oxide, and terbium oxide was usedwith indium of 0.8 in the mole ratio (In/(In+Sn+Zn)), tin of 0.1 in themole ratio (Sn/(In+Sn+Zn)), zinc of 0.1 in the mole ratio(Zn/(In+Sn+Zn)), and terbium of 0.06 in the mole ratio with respect tothe total metal (Tb/(In+Sn+Zn+Tb)). An organic EL device was fabricatedwith the rest of the fabrication condition the same as in the practicalexample 2-1. Incidentally, the anode layer 10 had an ionizationpotential of 5.84 eV. A direct-current voltage of 5.1 V was applied toacross the electrodes of the obtained organic EL device as in thepractical example 2-1, with the result that the current density was 165mA/cm² in value and the luminescence intensity was 95 nit. Theluminescent color was confirmed to be blue.

Practical Example 2-6

Instead of the target 2-1 of the practical example 2-1, a target 2-7made of indium oxide, tin oxide, zinc oxide, and holnium oxide was usedwith indium of 0.8 in the mole ratio (In/(In+Sn+Zn)), tin of 0.1 in themole ratio (Sn/(In+Sn+Zn)), zinc of 0.1 in the mole ratio(Zn/(In+Sn+Zn)), and holnium of 0.12 in the mole ratio with respect tothe total metal (Ho/(In+Sn+Zn+Ho)). An organic EL device was fabricatedwith the rest of the fabrication condition the same as in the practicalexample 2-1. Incidentally, the anode layer 10 had an ionizationpotential of 5.82 eV. A direct-current voltage of 5.1 V was applied toacross the electrodes of the obtained organic EL devices as in thepractical example 2-1, with the result that the current density was 2.0mA/cm² in value and the luminescence intensity was 166 nit. Theluminescent color was confirmed to be blue.

Practical Example 2-7

Instead of the target 2-1 of the practical example 2-1, a target 2-8 amade of indium oxide, tin oxide, zinc oxide, and cerium oxide was usedwith indium of 0.8 in the mole ratio (In/(In+Sn+Zn)), tin of 0.1 in themole ratio (Sn/(In+Sn+Zn)), zinc of 0.1 in the mole ratio(Zn/(In+Sn+Zn)), and cerium of 0.06 in the mole ratio with respect tothe total metal (Ce/(In+Sn+Zn+Ce)). An organic EL device was fabricatedwith the rest of the fabrication condition the same as in the practicalexample 2-1. Incidentally, the anode layer 10 had an ionizationpotential of 5.98 eV. A direct-current voltage of 4.9 V was applied toacross the electrodes of the obtained organic EL device as in thepractical example 2-1, with the result that the current density was 2.0mA/cm² in value and the luminescence intensity was 164 nit. Theluminescent color was confirmed to be blue.

Practical Example 2-8

Instead of the target 2-1 of the practical example 2-1, a target 2-8 bmade of indium oxide, tin oxide, and cerium oxide with indium of 0.9 inthe mole ratio (In/(In+Sn)) and tin of 0.1 in the mole ratio(Sn/(In+Sn)) was used to form a 75-nm-thick film on a substrate, onwhich a 20-nm-thick, film was made by using a target composed mainly ofzinc oxide with cerium of 0.05 in the mole ratio with respect to thetotal metal (Ce/(Zn+Ce)). An organic EL device was fabricated with therest of the fabrication condition the same as in the practical example2-1. Incidentally, the anode layer 10 had an ionization potential of6.18 eV and a transmittance of 79%. Moreover, a direct-current voltageof 4.8 V was applied to across the electrodes of the obtained organic ELdevice as in the practical example 2-1. Here, the current density was2.0 mA/cm² and the luminescence intensity was 162 nit (cd/m²). Theluminescent color was confirmed to be blue. Furthermore, for the sake ofdurability evaluation, constant-current driving was conducted at 10mA/cm². No particular leak current was found even after a lapse of 1000hours or more.

Comparative Example 2-1

Instead of the target 2-1 of the practical example 2-1, a target 2-9made of indium oxide, tin oxide, and zinc oxide was used with indium of0.6 in the mole ratio (In/(In+Sn+Zn)), tin of 0.3 in the mole ratio(Sn/(In+Sn+Zn)), and zinc of 0.1 in the mole ratio (Zn/(In+Sn+Zn)). Inother respects, the organic EL device was fabricated in the same manneras in the practical example 2-1. Incidentally, the anode layer 10 had anionization potential of 5.23 eV. A direct-current voltage of 6.0 V wasapplied to across the electrodes of the obtained organic EL device as inthe practical example 2-1, with the result that the current density was2.0 mA/cm² in value and the luminescence intensity was 166 nit. Theluminescent color was confirmed to be blue.

Summary of the Group of Embodiments 2

As has been detailed above, according to the organic EL device of thepresent invention, it has become possible to provide an organic ELdevice which has excellent transparency and durability and exhibits highluminescence intensity even under a low driving voltage, comprising theanode layer and the like made of certain organic compounds. It was alsoconfirmed that the anode layer and the like made of certain inorganiccompounds had excellent etching properties.

Moreover, according to the substrate for an organic EL device of thepresent invention, an organic EL device exhibiting such preferableperformance can be fabricated easily.

Besides, according to the method of fabricating an organic EL device ofthe present invention, it has become possible to provide an organic ELdevice effectively which has excellent transparency and durability andexhibits high luminescence intensity even under a low driving voltage.

Group of Embodiments 3

Hereinafter, embodiments pertaining to the third group of invention willbe described with reference to the drawings.

Practical Example 3-1 (1) Preparation for the Fabrication of a Substratefor an Organic EL Device (Fabrication of a Target)

Initially, a sputtering target to be used in forming electrodes of anorganic EL device by sputtering is fabricated.

Initially, powders of indium oxide and cerium oxide (no greater than 1μm in average particle diameter) were accommodated in a wet ball millcontainer, and mixed and ground for 72 hours. Here, the mixing andgrinding are performed so that cerium oxide is 0.05 in the mole ratiowith respect to the total amount (this mole ratio will be expressed asCe/(In+Ce)).

Next, the resulting ground article was granulated, followed by pressmolding to dimensions of 4 inches in diameter and 5 mm in thickness. Theresultant was accommodated in a baking furnace, and then heated andbaked at a temperature of 1400° C. for 36 hours to fabricate a target3-1 for an anode layer.

Incidentally, the present embodiment 3 will deal with an organic ELdevice. This organic EL device corresponds to an example of the organicelectroluminescence apparatus in claims.

(2) Formation of the Anode Layer

Then, a transparent glass substrate 310 of 1.1 mm in thickness, 25 mm inwidth, and 75 mm in length, the foregoing target 3-1 fabricated, and anAg target (Ag: 98.5 wt %, Pd: 0.5 wt %, Cu: 1.0 wt %) are placed in thecommon vacuum chamber of the high frequency sputtering system and thevacuum evaporator.

Then, the high frequency sputtering system was operated to form a35-nm-thick metal oxide layer 312 a, a 5-nm-thick Ag thin film 14, and a35-nm-thick metal oxide layer 312 b on the glass substrate 310. In thisway, an electrode substrate 318 having an anode layer 316 composed ofthese three layers was obtained. This is shown in FIG. 1.

Here, the glass substrate 310 corresponds to an example of the “basemember” in claims. While this practical example uses the glass substrate310, it is possible to use a plastic substrate or such a substrate as asilicon wafer, depending on the applications. Besides, the step offorming an anode layer by such sputtering corresponds to an example of“forming an electrode by sputtering” in claims. That is, the anode layer316 corresponds to an example of the “electrode” in claims.

Here, a mixed gas of argon gas and oxygen gas was filled in a statedepressurized down to 5×10⁻⁴ Pa in vacuum. In that atmosphere, thesputtering was performed under the condition of: an ultimate vacuum of3×10⁻¹ Pa; a substrate temperature of 25° C.; an input voltage of 100 W;and a film forming time of 14 minutes.

Hereinafter, the electrode substrate 318 combining this glass substrate310 and the anode layer 316 will be referred to simply as substrate 318.This substrate 318 corresponds to an example of the electrode substratefor an organic electroluminescence apparatus in claims.

Subsequently, this substrate 318 was subjected to ultrasonic cleaning inisopropyl alcohol, and then dried in a N₂ (nitrogen gas) atmospherebefore 10-minute cleaning by using UV (ultraviolet rays) and ozone.

(3) Measurements

Before and after the UV cleaning of the substrate, the anode layer 316was measured for the value of its work function by using AC-1 (fromRiken Keiki Co., Ltd.), and found to be 5.85 eV (before cleaning) and6.20 eV (after cleaning). Moreover, the substrate provided with theanode layer 316 was measured for light transmittance (wavelength of 550nm) and found to be 84%. The surface resistance was measured by the fourprobe method and found to be 4.6 Ω/sq.

(4) Formation of the Organic EL Device

Next, the foregoing “substrate” was loaded on the substrate holder inthe vacuum chamber of the vacuum evaporator. Then, the vacuum chamberwas depressurized inside to a vacuum of 1×10⁻⁶ Torr or lower before ahole transporting layer 320, an organic luminescent layer 322, anelectron injection layer 324, and a cathode layer 326 were laminated insuccession on the anode layer 316 of the substrate 318 to obtain anorganic EL device. This is shown in FIG. 2.

Here, in the period from the formation of the hole transporting layer320 to the formation of the cathode layer 326, the vacuum was not brokeneven once so that the same vacuum condition was maintained.

The step of forming the organic luminescent layer 322 by such vacuumdeposition corresponds to an example of “forming an organicelectroluminescence layer by vacuum deposition” in claims. That is, theorganic luminescent layer 322 corresponds to an example of the “organicelectroluminescence layer” in claims.

Initially, as the hole transporting material 320, TBDB wasvacuum-evaporated to 60 nm. Next, as the organic luminescent layer 322,DPVDPAN and D1 were co-evaporated to 40 nm in the vacuum. Here, thedeposition rate of the DPVDPAN was 40 nm/s and the deposition rate of D1was 1 nm/s.

Then, as the electron injection layer 324, Alq was vacuum-evaporated to20 nm. Finally, Al and Li were vacuum-evaporated to form the cathodelayer 326 on the electron injection layer 324, thereby fabricating theorganic EL device 30. Incidentally, the deposition rate of Al here was 1nm/s, and the deposition rate of Li was 0.01 nm/s. The thickness of theAl/Li film was 200 nm.

The chemical formulae of TBDB, DPVDPAN, D1, and Alq are shown in FIG.19.

(5) Evaluation on the Organic EL Device Fabricated

A direct-current voltage of 4.3 V was applied to across electrodes withthe cathode layer 326 of the obtained organic EL device 330 as thenegative (−) electrode and the anode layer 316 as the positive (+)electrode. Here, the current density was 2.0 mA/cm² and the luminescenceintensity was 160 nit (cd/m²). The luminescent color was confirmed to beblue. Furthermore, for the sake of durability evaluation,constant-current driving was conducted at 10 mA/cm². No particular leakcurrent was found even after a lapse of 1000 hours or more.

The results of the practical example 3-1 are shown in Table 3-1.

TABLE 3-1 Practical Practical Practical Practical embodiment embodimentembodiment embodiment 3-1 3-2 3-3 3-4 Material of anode layer In oxide/In oxide/ In oxide/ In oxide/ Ce oxide/ Sn oxide/ Sn oxide/ Sn oxide/ Znoxide/ Zn oxide/ Zn oxide/ Nd oxide/ Sm oxide/ Pr oxide/ Work function(eV) (before cleaning) 5.85 5.81 5.84 5.80 Work function (eV) (aftercleaning) 6.20 8.85 5.95 5.85 Thickness (nm) oxide/Ag/oxide 35/5/3535/5/35 35/5/35 35/5/35 Light transmittance (%) * 85 85 84 84 Surfaceresistance (Ω/□) 4.6 4.3 3.9 4.0 Hole transporting material TBDB TBDBTBDB TBDB Thickness (nm) 60 60 60 60 Material of luminescent layerDPVDPAN DPVDPAN DPVDPAN DPVDPAN Thickness (nm) 40 40 40 40 Materialelectron injection layer Alq Alq Alq Alq Thickness (nm) 20 20 20 20Material of cathode layer Al/Li Al/Li Al/Li Al/Li Thickness (nm) 200 200200 200 Voltage (V) 4.3 4.8 4.5 4.6 Luminescence Intensity (cd/m²) 160156 164 161 Half life 1000 hours 1000 hours 1000 hours 1000 hours ormore or more or more or more * Glass reference

Practical Example 3-2

A target 3-3 shown below was used instead of the target 3-1 of thepractical example 3-1. This target 3-3 is one made of indium oxide, tinoxide, zinc oxide, and neodymium oxide, having the following specificcomposition.

Here, indium oxide, tin oxide, and zinc oxide will be referred to asmain metal components.

Initially, the mole ratio of indium in the main metal components(expressed as In/(In+Sn+Zn)) is 0.8. The mole ratio of tin in the mainmetal components (expressed as Sn/(In+Sn+Zn)) is 0.1. The mole ratio ofzinc in the main metal components (expressed as Zn/(In+Sn+Zn)) is 0.1.In addition, the mole ratio of neodymium in the total metal (expressedas Nd/(In+Sn+Zn+Nd)) is 0.06.

The organic EL device 330 was fabricated as in the foregoing practicalexample 3-1 except that the target 3-3 was used instead of the target3-1.

Incidentally, at the time of fabrication, the anode layer 316 showedwork functions of 5.81 eV (before cleaning) and 5.85 eV (aftercleaning). The surface resistance of the anode layer 316 was 4.3 Ω/sq.

Moreover, a direct-current voltage of 4.8 V was applied to across theelectrodes of the obtained organic EL device 330 as in the practicalexample 3-1, with the result that the current density was 2.0 mA/cm² invalue and the luminescence intensity was 156 nit. The luminescent colorwas confirmed to be blue. Furthermore, for the sake of durabilityevaluation, constant-current driving was conducted at 10 mA/cm². Noparticular leak current was found even after a lapse of 1000 hours ormore.

Incidentally, the results of the practical example 3-2 are also shown inTable 3-1.

Practical Example 3-3

A target 3-4 shown below was used instead of the target 3-1 of thepractical example 3-1. This target 3-4 is one made of indium oxide, tinoxide, zinc oxide, and samarium oxide, having the specific compositionas follows:

The mole ratio of indium in the main metal components (In/(In+Sn+Zn)) is0.8. The mole ratio of tin in the main metal components (Sn/(In+Sn+Zn))is 0.1. The mole ratio of zinc in the main metal components(Zn/(In+Sn+Zn)) is 0.1. In addition, the mole ratio of samarium in thetotal metal (this mole ratio will be expressed as Sm/(In+Sn+Zn+Sm)) is0.04.

The organic EL device 330 was fabricated as in the foregoing practicalexample 3-1 except that the target 3-4 was used instead of the target3-1.

Incidentally, the anode layer 316 showed work functions of 5.84 eV(before cleaning) and 5.95 eV (after cleaning). The surface resistanceof the anode layer 316 was 3.9 Ω/sq. A direct-current voltage of 4.5 Vwas applied to across the electrodes of the obtained organic EL device330 as in the practical example 3-1, with the result that the currentdensity was 2.0 mA/cm² in value and the luminescence intensity was 164nit. The luminescent color was confirmed to be blue. Furthermore, forthe sake of durability evaluation, constant-current driving wasconducted at 10 mA/cm². No particular leak current was found even aftera lapse of 1000 hours or more.

Incidentally, the results of the practical example 3-3 are also shown inTable 3-1.

Practical Example 3-4

A target 3-5 shown below was used instead of the target 3-1 of thepractical example 3-1. This target 3-5 is one made of indium oxide, tinoxide, zinc oxide, and praseodymium oxide, having the specificcomposition as follows:

The mole ratio of indium in the main metal components (In/(In+Sn+Zn)) is0.8. The mole ratio of tin in the main metal components (Sn/(In+Sn+Zn))is 0.1. The mole ratio of zinc in the main metal components(Zn/(In+Sn+Zn)) is 0.1. In addition, the mole ratio of praseodymium inthe total metal (Pr/(In+Sn+Zn+Pr)) is 0.04.

The organic EL device 330 was fabricated as in the foregoing practicalexample 3-1 except that the target 3-5 was used instead of the target3-1. Incidentally, the anode layer 316 showed work functions of 5.80 eV(before cleaning) and 5.85 eV (after cleaning). The surface resistanceof the anode layer 316 was 4.01/sq.

A direct-current voltage of 4.6 V was applied to across the electrodesof the obtained organic EL device 330 as in the practical example 3-1,with the result that the current density was 2.0 mA/cm² in value and theluminescence intensity was 161 nit. The luminescent color was confirmedto be blue. Furthermore, for the sake of durability evaluation,constant-current driving was conducted at 10 mA/cm². No particular leakcurrent was found even after a lapse of 1000 hours or more.

Incidentally, the results of the practical example 3-4 are also shown inTable 3-1.

Practical Example 3-5

A target 3-6 shown below was used instead of the target 3-1 of thepractical example 3-1. This target 3-6 is one made of indium oxide, tinoxide, zinc oxide, and tantalum oxide, having the specific compositionas follows:

The mole ratio of indium in the main metal components (In/(In+Sn+Zn)) is0.8. The mole ratio of tin in the main metal components (Sn/(In+Sn+Zn))is 0.1. The mole ratio of zinc in the main metal components(Zn/(In+Sn+Zn)) is 0.1. In addition, the mole ratio of tantalum in thetotal metal (Ta/(In+Sn+Zn+Ta)) is 0.06.

The organic EL device 330 was fabricated as in the foregoing practicalexample 3-1 except that the target 3-6 was used instead of the target3-1. Incidentally, the anode layer 316 showed work functions of 5.60 eV(before cleaning) and 5.64 eV (after cleaning). The surface resistanceof the anode layer 316 was 4.8 Ω/sq.

A direct-current voltage of 5.1 V was applied to across the electrodesof the obtained organic EL device 330 as in the practical example 3-1,with the result that the current density was 162 mA/cm² in value and theluminescence intensity was 62 nit. The luminescent color was confirmedto be blue. Furthermore, for the sake of durability evaluation,constant-current driving was conducted at 10 mA/cm². No particular leakcurrent was found even after a lapse of 1000 hours or more.

Incidentally, the results of the practical example 3-5 are shown inTable 3-2.

TABLE 3-2 Practical Practical Practical Practical embodiment embodimentembodiment embodiment 3-5 3-6 3-7 3-8 Material of anode layer In oxide/In oxide/ In oxide/ In oxide/ Sn oxide/ Sn oxide/ Sn oxide/ Sn oxide/ Znoxide/ Zn oxide/ Zn oxide/ Zn oxide/ Ta oxide/ Nb oxide/ Hf oxide/ Smoxide/ Work function (eV) (before cleaning) 5.60 5.64 5.61 5.72 Workfunction (eV) (after cleaning) 5.64 5.71 5.65 5.95 Thickness (nm)35/5/35 35/5/35 35/5 35/100/35 oxide/Ag/oxide Light transmittance (%) *83 83 83 Surface resistance (Ω/□) 5.3 4.8 5.6 0.2 Hole transportingmaterial TBDB TBDB TBDB TBDB Thickness (nm) 60 60 60 60 Material ofluminescent layer DPVDPAN DPVDPAN/ DPVDPAN/ DPVDPAN/ D1 D1 D1 D1Thickness (nm) 40 40 40 40 Material electron injection layer Alq Alq AlqAlq Thickness (nm) 20 20 20 20 Material of cathode layer Al/Li Al/LiAl/Li Mg/Ag In oxide/ Zn oxide Thickness (nm) 200 200 200 5 75 (Totalthickness: 80) Voltage (V) 4.8 4.7 4.8 4.4 Luminescence intensity(cd/m²) 162 165 163 166 Half life 1000 hours 1000 hours 1000 hours 1000hours or more or more or more or more * Transmittance: Glass reference

Practical Example 3-6

A target 3-7 shown below was used instead of the target 3-1 of thepractical example 3-1. This target 3-7 is one made of indium oxide, tinoxide, zinc oxide, and niobium oxide, having the specific composition asfollows:

The mole ratio of indium in the main metal components (In/(In+Sn+Zn)) is0.8. The mole ratio of tin in the main metal components (Sn/(In+Sn+Zn))is 0.1. The mole ratio of zinc in the main metal components(Zn/(In+Sn+Zn)) is 0.1. In addition, the mole ratio of niobium in thetotal metal (Nb/(In+Sn+Zn+Nb)) is 0.12.

The organic EL device 330 was fabricated as in the foregoing practicalexample 3-1 except that the target 3-7 was used instead of the target3-1.

Incidentally, the anode layer 316 showed work functions of 5.64 eV(before cleaning) and 5.71 eV (after cleaning). The surface resistanceof the anode layer 316 was 4.8 Ω/sq.

A direct-current voltage of 5.1 V was applied to across the electrodesof the obtained organic EL device 330 as in the practical example 3-1,with the result that the current density was 2.0 mA/cm² in value and theluminescence intensity was 166 nit. The luminescent color was confirmedto be blue. Furthermore, for the sake of durability evaluation,constant-current driving was conducted at 10 mA/cm². No particular leakcurrent was found even after a lapse of 1000 hours or more.

Incidentally, the results of the practical example 3-6 are also shown inTable 3-2.

Practical Example 3-7

A target 3-8 shown below was used instead of the target 3-1 of thepractical example 3-1. This target 3-8 is one made of indium oxide, tinoxide, zinc oxide, and hafnium oxide, having the specific composition asfollows:

The mole ratio of indium in the main metal components (In/(In+Sn+Zn)) is0.8. The mole ratio of tin in the main metal components (Sn/(In+Sn+Zn))is 0.1. The mole ratio of zinc in the main metal components(Zn/(In+Sn+Zn)) is 0.1. In addition, the mole ratio of hafnium in thetotal metal (Hf/(In+Sn+Zn+Hf)) is 0.06.

The organic EL device 330 was fabricated as in the foregoing practicalexample 3-1 except that the target 3-8 was used instead of the target3-1. Incidentally, the anode layer 316 showed work functions of 5.61 eV(before cleaning) and 5.65 eV (after cleaning). The surface resistanceof the anode layer 316 was 5.6 Ω/sq.

A direct-current voltage of 4.8 V was applied to across the electrodesof the obtained organic EL device 330 as in the practical example 3-1,with the result that the current density was 2.0 mA/cm² in value and theluminescence intensity was 163 nit. The luminescent color was confirmedto be blue. Furthermore, for the sake of durability evaluation,constant-current driving was conducted at 10 mA/cm². No particular leakcurrent was found even after a lapse of 1000 hours or more.

Incidentally, the results of the practical example 3-7 are also shown inTable 3-2.

Practical Example 3-8

The target 3-4 of the practical example 3-3 was used to form the anodelayer 316 with thicknesses of an oxide layer: 35 nm, a metal layer: 100nm, and an oxide layer: 35 nm. Moreover, the cathode layer was given thecomposition of an Mg/Ag thickness: 5 nm and a transparent conductivefilm made of indium oxide and zinc oxide (In/(In+Zn))=0.85): 75 nm.Here, In/(In+Zn) represents the mole ratio of indium with respect to thetotal amount of indium and zinc. In other respects, the organic ELdevice 330 was fabricated in the same manner as in the practical example3-1.

The anode layer 316 showed work functions of 5.72 eV (before cleaning)and 5.95 eV (after cleaning). The surface resistance of the anode layer316 was 0.2 Ω/sq.

A direct-current voltage of 4.4 V was applied to across the electrodesof the obtained organic EL device 330 as in the practical example 3-1,with the result that the current density was 2.0 mA/cm² in value and theluminescence intensity was 166 nit. The luminescent color was confirmedto be blue. Furthermore, for the sake of durability evaluation,constant-current driving was conducted at 10 mA/cm². No particular leakcurrent was found even after a lapse of 1000 hours or more.

Incidentally, the results of the practical example 3-8 are also shown inTable 3-2.

Comparative Example 3-1

A target 3-9 made of indium oxide, tin oxide, and zinc oxide was usedinstead of the target 3-1 of the practical example 3-1. The specificcomposition of the target 3-9 is as follows:

In the target 3-9, the mole ratio of indium in the main metal components(In/(In+Sn+Zn)) is 0.6. The mole ratio of tin in the main metalcomponents (Sn/(In+Sn+Zn)) is 0.3. The mole ratio of zinc in the mainmetal components (Zn/(In+Sn+Zn)) is 0.1. The organic EL device 330 wasfabricated in the same manner as in the practical example 3-1 exceptthat this target 3-9 was used.

Incidentally, the anode layer 316 showed work functions of 4.65 eV(before cleaning) and 5.23 eV (after cleaning). A direct-current voltageof 6.0 V was applied to across the electrodes of the obtained organic ELdevice 330 as in the practical example 3-1, with the result that thecurrent density was 2.0 mA/cm² in value and the luminescence intensitywas 166 nit. The luminescent color was confirmed to be blue.

Incidentally, the results of the comparative example 3-1 are shown inTable 3-3.

TABLE 3-3 Comparative Comparative example example 3-1 3-2 Material ofanode layer In oxide/ Ce oxide/ Sn oxide/ Zn oxide/ Work function (eV)(before cleaning) 4.65 5.25 Work function (eV) (after cleaning) 5.235.46 Thickness (nm) 75 oxide/Ag/oxide 35/5/35 Light transmittance (%) *89 Surface resistance (Ω/□) 15.8 N/A Hole transporting material TBDBTBDB Thickness (nm) 60 60 Material of luminescent layer DPVDPAN/DPVDPAN/ D1 D1 Thickness (nm) 40 40 Material electron injection layerAlq Alq Thickness (nm) 20 20 Material of cathode layer Al/Li Al/LiThickness (nm) 200 200 Voltage (V) 6.0 Luminescence intensity 166(cd/m²) Half life * Transmittance: Glass reference

Comparative Example 3-2

A target of 100% cerium oxide was used instead of the target 3-1 of thepractical example 3-1. In other respects, the film formation wasperformed in the same manner as in the practical example 3-1.

As a result, the anode layer 316 showed work functions of 5.25 eV(before cleaning) and 5.46 eV (after cleaning). As for the surfaceresistance, the anode layer 316 had an insulative surface and could notbe measured.

Incidentally, the results of the comparative example 3-2 are also shownin Table 3-3.

Summary of the Group of Embodiments 3

As has been detailed above, according to the organic EL device of thepresent invention, it has become possible to provide an organic ELdevice which has excellent transparency and durability and exhibits highluminescence intensity even under a low driving voltage, comprisingelectrodes (such as the anode layer) made of certain inorganiccompounds.

It was also confirmed that the anode layer and the like made of certaininorganic compounds described in the present invention caused nodeterioration in etching property.

Besides, according to the organic EL device of the present invention, ithas become possible to provide an organic EL device effectively whichhas excellent transparency and durability and exhibits high luminescenceintensity even under a low driving voltage.

Moreover, according to the electrode substrate of the present invention,it is possible to fabricate an organic EL device which provides theforegoing effects.

Furthermore, according to the fabrication method of the presentinvention, it is possible to fabricate an organic EL device whichprovides the foregoing effects.

Group of Embodiments 4

Hereinafter, a group of preferred embodiments 4 of the present inventionwill be described with reference to the drawings.

Practical Example 4-1 (1) Preparation for the Fabrication of a Substratefor an Organic EL Device (Fabrication of Targets)

Initially, powders of indium oxide, tin oxide, and cerium oxide areaccommodated in a wet ball mill container so that the mole ratio ofindium (In/(In+Sn)) is 0.9, the mole ratio of tin (Sn/(In+Sn)) is 0.1,and the mole ratio of cerium to the total metal (Ce/(In+Sn+Ce)) is 0.05,followed by mixing and grinding for 72 hours.

Then, the resulting ground article was granulated, and press molded todimensions of 4 inches in diameter and 5 mm in thickness. The resultantwas accommodated in a baking furnace, and then heated and baked at atemperature of 1400° C. for 36 hours to fabricate a target 4-1 for athin film layer of a metal oxide.

In addition, powders of indium oxide and zinc oxide (no greater than 1μm in average particle diameter) were accommodated in a wet ball millcontainer so that the mole ratio Zn/(In+Zn) was 0.15, followed by mixingand grinding for 72 hours.

Then, the resulting ground article was granulated, and press molded todimensions of 4 inches in diameter and 5 mm in thickness. The resultantwas accommodated in a baking furnace, and then heated and baked at atemperature of 1400° C. for 36 hours to fabricate an IZO target for theanode layer.

Next, a metal target of Ag with additional Cu of 0.7 wt % and Au of 0.8wt % was fabricated. This will be referred to as an Ag target.

Besides, a metal target of Cu with additional Ni of 1.7 wt % and Co of1.3 wt % was fabricated. This will be referred to as a Cu target.Moreover, a metal target of pure Al will be referred to as an Al target.

(2) Fabrication of the Substrate for an Organic EL Device

Next, description will be given of the formation of the substrate for anorganic EL device. This is shown in FIG. 12.

A transparent glass substrate 410 of 1.1 mm in thickness, 25 mm inwidth, and 75 mm in length, and the fabricated target 4-1, IZO target,and Al target are placed in the vacuum chamber of the high frequencysputtering system. The high frequency sputtering system is operated todepressurize down to an ultimate vacuum of 5×10⁻⁴ Pa, in which stateargon gas alone is filled. FIG. 12(1) shows the glass substrate 410,which corresponds to an example of the “base member” in claims.

In that atmosphere, sputtering was performed under the condition of: avacuum of 3×10⁻¹ Pa; a substrate temperature at room temperatures; aninput voltage of 100 W; and a film forming time of 14 minutes, so that a110-nm-thick thin film layer 412 of a metal oxide was formed by usingthe target 4-1 in the argon gas. This is shown in FIG. 12(2).

Subsequently, the Al target was used to form a 120-nm-thick Al thin film414 in the argon gas. This is shown in FIG. 12(3).

Moreover, the IZO target was used to form a 20-nm-thick IZO thin film416 in the argon gas mixed with oxygen gas. This is shown in FIGS. 12(4)and 13.

Incidentally, the IZO thin film 416, a protective film, need notnecessarily be formed on the foregoing Al thin film 414, but ispreferably formed.

Subsequently, in a nitrate-phosphate-acetate aqueous solution, the IZOthin film/Al thin film were etched to form IZO/Al thin wires 418 of 20μm in width. This is shown in FIG. 12(5).

Thereafter, the thin film layer of the metal oxide formed from thetarget 4-1 on this substrate was etched in an oxalic aqueous solution toform such a pattern that one IZO/Al thin wire 418 falls on the side of athin film electrode made from the target 4-1. The electrode fabricatedthrough such patterning will be referred to as a patterning electrode.This is shown in FIG. 12(6).

Incidentally, the thin film layer of the metal oxide formed from thetarget 4-1 preferably has a width of 90 μm. Moreover, the Al thin wires414 obtained through the foregoing etching correspond to an example ofthe metal thin wire. Besides, the IZO/Al thin wire 418 corresponds to anexample where a protective film is arranged on a metal thin wire.

This substrate was subjected to ultrasonic cleaning in isopropylalcohol, and then dried in a N₂ (nitrogen gas) atmosphere before10-minute cleaning by using UV (ultraviolet rays) and ozone.

(3) Measurements

The patterning electrode (electrode width: 90 μm, electrode length: 100mm) described above was measured for resistance by the two probe method,and found to be 2.5 kΩ. The metal-oxide thin film layer 412 formed fromthe target 4-1 alone was 3×10 E-3 Ωcm in specific resistance. Moreover,the patterning electrode was measured for light transmittance(wavelength of 550 nm) and found to be 89%. After the UV cleaning of thesubstrate, the anode layer 412 was measured for the value of its workfunction by using AC-1 (from Riken Keiki Co., Ltd.), and found to be6.06 eV.

Incidentally, the measurements are shown in Table 4-1.

(4) Formation of the Organic EL Device

The foregoing “substrate” was loaded on the substrate holder in thevacuum chamber of the vacuum evaporator. Then, the vacuum chamber wasdepressurized inside to a vacuum of 1×10⁻⁶ Torr or lower before a holetransporting layer 426, an organic luminescent layer 428, an electroninjection layer 430, and a cathode layer 432 were laminated insuccession on the anode layer 412 of the substrate to obtain an organicEL device 434. This is shown in FIG. 14.

Here, in the period from the formation of the organic luminescent layer428 to the formation of the cathode layer 432, the vacuum was not brokeneven once so that the same vacuum condition was maintained.

Here, the organic EL device 434 corresponds to the organicelectroluminescence device in claims.

Initially, as the hole transporting material, TBDB was vacuum-evaporatedto 60 nm. Next, as the organic luminescent layer 428, DPVDPAN and D1were co-evaporated to 40 nm in the vacuum. Here, the deposition rate ofthe DPVDPAN was 40 nm/s and the deposition rate of D1 was 1 nm/s.

Then, as the electron injection layer 430, Alq was vacuum-evaporated to20 nm. Finally, Al and Li were vacuum-evaporated to form the cathodelayer 430 on the electron injection layer 432, thereby fabricating theorganic EL device 434.

Here, the deposition rate of Al was 1 nm/s, and the deposition rate ofLi was 0.01 nm/s. The thickness of the Al/Li film was 200 nm.

Incidentally, these are shown in Table 4-1. Moreover, the chemicalformulae of TBDB, DPVDPAN, D1, and Alq are shown in FIG. 19.

(5) Evaluation on the Organic EL Device Fabricated

A direct-current voltage of 4.4 V was applied to across electrodes withthe cathode layer 432 of the obtained organic EL device 434 as thenegative (−) electrode and the anode layer 412 as the positive (+)electrode.

Here, the current density was 2.0 mA/cm² and the luminescence intensitywas 161 nit (cd/m²). The luminescent color was confirmed to be blue.

Furthermore, for the sake of durability evaluation, constant-currentdriving was conducted at 10 mA/cm². No particular leak current was foundeven after a lapse of 1000 hours or more.

Incidentally, the results of the practical example 4-1 are shown inTable 4-1.

TABLE 4-1 Practical Practical Practical Practical embodiment embodimentembodiment embodiment 4-1 4-2 4-3 4-4 Material of anode layer In oxide/In oxide/ In oxide/ In oxide/ Sn oxide/ Sn oxide/ Sn oxide/ Zn oxide/ Ceoxide Ce oxide Ce oxide Sm oxide (Auxiliary wiring) Al Al Al AgProtective layer of metal oxide IZO IZO — — IP(eV) (after cleaning) 6.055.85 5.85 5.90 Light transmittance (% * 89 89 89 89 Electrode resistance(kΩ) 2.5 2.4 2.4 2.4 Specific resistance of anode layer 3 × 10E−3 8 ×10E−4 8 × 10E−4 7 × 10E−4 (Ω cm) Hole transporting material TBDB TBDBTBDB TBDB Thickness (nm) 60 60 60 60 Material of luminescent layerDPVDPAN DPVDPAN DPVDPAN DPVDPAN Thickness (nm) 40 40 40 40 Materialelectron injection layer Alq Alq Alq Alq Thickness (nm) 20 20 20 20Material of cathode layer Al/Li Al/Li Al/Li Al/Li Thickness (nm) 200 200200 200 Voltage (V) 4.4 4.3 4.4 4.4 Luminescence intensity (cd/m²) 161164 163 156 Half life 1000 hours 1000 hours 1000 hours 1000 hours ormore or more or more or more * Glass reference

Practical Example 4-2

A target 4-2 shown below was used instead of the target 4-1 of thepractical example 4-1. The organic EL device 434 was fabricated in thesame manner as in the practical example 4-1 except that the target 4-2was used.

The target 4-2 is composed of indium oxide, tin oxide, and cerium oxide.The mole ratio of indium (In/(In+Sn)) is 0.9, the mole ratio of tin(Sn/(In+Sn)) is 0.1, and the mole ratio of cerium to the total metal(Ce/(In+Sn+Ce)) is 0.03.

Incidentally, the work function of the anode layer was 5.85 eV in value.The electrode resistance was 2.4 kΩ.

A direct-current voltage of 4.3 V was applied to across the electrodesof the organic EL device 434 obtained by the foregoing means as in thepractical example 4-1, with the result that the current density was 2.0mA/cm² in value and the luminescence intensity was 164 nit. Theluminescent color was confirmed to be blue. Furthermore, for the sake ofdurability evaluation, constant-current driving was conducted at 10mA/cm². No particular leak current was found even after a lapse of 1000hours or more.

Incidentally, the results of the practical example 4-2 are also shown inTable 4-1.

Practical Example 4-3

The organic EL device 434 was fabricated in the same manner as in thepractical example 4-2 except that the protective film made of the IZOtarget in the practical example 4-2 was not used.

Incidentally, the work function of the anode layer was 5.85 eV in value.The electrode resistance was 2.4 kΩ.

A direct-current voltage of 4.4 V was applied to across the electrodes,with the result that the current density was 2.0 mA/cm² in value and theluminescence intensity was 163 nit. The luminescent color was confirmedto be blue. Furthermore, for the sake of durability evaluation,constant-current driving was conducted at 10 mA/cm². No particular leakcurrent was found even after a lapse of 1000 hours or more.

Incidentally, the results of the practical example 4-3 are also shown inTable 4-1.

Practical Example 4-4

A target 4-4 shown below was used instead of the target 4-1 of thepractical example 4-1. As for the metal target, an Ag target was usedinstead of the Al target. Incidentally the IZO protective film 416 isnot used. The organic EL device 434 was fabricated otherwise in the samemanner as in the practical example 4-1.

The target 4-4 is composed of indium oxide, tin oxide, and samariumoxide. The mole ratio of indium (In/(In+Zn)) is 0.9, the mole ratio oftin (Sn/(In+Sn)) is 0.1, and the mole ratio of samarium to the totalmetal (Sm/(In+Zn+Sm)) is 0.03.

Incidentally, the work function of the anode layer 412 was 5.90 eV invalue. The electrode resistance was 2.4 kΩ.

A direct-current voltage of 4.4 V was applied to across the electrodesof the organic EL device 434 obtained by the foregoing means as in thepractical example 4-1, with the result that the current density was 2.0mA/cm² in value and the luminescence intensity was 156 nit. Theluminescent color was confirmed to be blue. Furthermore, for the sake ofdurability evaluation, constant-current driving was conducted at 10mA/cm². No particular leak current was found even after a lapse of 1000hours or more.

Incidentally, the results of the practical example 4-4 are also shown inTable 4-1.

Practical Example 4-5

A target 4-5 was used instead of the target 4-1 of the practical example4-1. As for the metal target, an Ag target was used instead of the Altarget. The organic EL device 434 was fabricated otherwise under thesame condition as in the practical example 4-1.

The target 4-5 is composed of indium oxide, zinc oxide, and praseodymiumoxide. The mole ratio of indium (In/(In+Zn)) is 0.9, the mole ratio oftin (Sn/(In+Zn)) is 0.1, and the mole ratio of praseodymium to the totalmetal (Pr/(In+Sn+Pr)) is 0.04.

Incidentally, the work function of the anode layer 412 was 5.81 eV invalue. The electrode resistance was 2.5 kΩ.

A direct-current voltage of 4.5 V was applied to across the electrodesof the obtained organic EL device 434 as in the practical example 4-1,with the result that the current density was 2.0 mA/cm² in value and theluminescence intensity was 161 nit. The luminescent color was confirmedto be blue. Furthermore, for the sake of durability evaluation,constant-current driving was conducted at 10 mA/cm². No particular leakcurrent was found even after a lapse of 1000 hours or more.

Incidentally, the results of the practical example 4-5 are shown inTable 4-2.

TABLE 4-2 Practical Practical Practical Comparative embodimentembodiment embodiment example 4-5 4-6 4-7 4-1 Material of anode layer Inoxide/ In oxide/ In oxide/ In oxide/ Sn oxide/ Sn oxide/ Sn oxide/ Snoxide/ Pr oxide Nd oxide/ Tb oxide (Auxiliary wiring) Ag Cu Ag AgProtective layer of metal oxide IZO IZO IZO IP (eV) (after cleaning)5.81 5.80 5.90 5.25 Light transmittance (%)* 89 87 87 90 Electroderesistance (kΩ) 2.5 2.6 2.5 2.4 Specific resistance of anode layer 2 ×10E−3 7 × 10E−3 4 × 10E−2 4 × 10E−4 (Ω cm) Hole transporting materialTBDB TBDB TBDB TBDB Thickness (nm) 60 60 60 60 Material of luminescentlayer DPVDPAN DPVDPAN/ DPVDPAN/ DPVDPAN/ D1 D1 D1 D1 Thickness (nm) 4040 40 40 Material electron injection layer Alq Alq Alq Alq Thickness(nm) 20 20 20 20 Material of cathode layer Al/Li Al/Li Al/Li Al/LiThickness (nm) 200 200 200 200 Voltage (V) 4.5 4.5 4.6 5.3 Luminescenceintensity (cd/m²) 161 158 166 162 Half life 1000 hours 1000 hours 1000hours or more or more or more * Transmittance: Glass reference

Practical Example 4-6

A target 4-6 was used instead of the target 4-1 of the practical example4-1. As for the metal target, a Cu target was used instead of the Altarget. In other respects, the organic EL device 434 was fabricated asin the practical example 4-1.

The target 4-6 is composed of indium oxide, tin oxide, and neodymiumoxide. The mole ratio of indium (In/(In+Sn)) is 0.9, the mole ratio oftin (Sn/(In+Sn)) is 0.1, and the mole ratio of neodymium to the totalmetal (Nd/(In+Sn+Nd)) is 0.06.

Incidentally, the work function of the anode layer 412 was 5.80 eV invalue. The electrode resistance was 2.6 kΩ.

A direct-current voltage of 4.5 V was applied to across the electrodesof the obtained organic EL device 434 as in the practical example 4-1,with the result that the current density was 2.0 mA/cm² in value and theluminescence intensity was 158 nit. The luminescent color was confirmedto be blue. Furthermore, for the sake of durability evaluation,constant-current driving was conducted at 10 mA/cm². No particular leakcurrent was found even after a lapse of 1000 hours or more.

Incidentally, the results of the practical example 4-6 are also shown inTable 4-2.

Practical Example 4-7

A target 4-7 was used instead of the target 4-1 of the practical example4-1. As for the metal target, an Ag target was used instead of the Altarget. In other respects, the organic EL device 434 was fabricated asin the practical example 4-1.

The target 4-7 is composed of indium oxide, tin oxide, and terbiumoxide. The mole ratio of indium (In/(In+Sn)) is 0.9, the mole ratio oftin (Sn/(In+Sn)) is 0.1, and the mole ratio of terbium to the totalmetal (Tb/(In+Sn+Tb)) is 0.06.

Incidentally, the work function of the anode layer 412 was 5.90 eV invalue. The electrode resistance was 2.5 kΩ.

A direct-current voltage of 4.6 V was applied to across the electrodesof the obtained organic EL device 434 as in the practical example 4-1,with the result that the current density was 2.0 mA/cm² in value and theluminescence intensity was 166 nit. The luminescent color was confirmedto be blue. Furthermore, for the sake of durability evaluation,constant-current driving was conducted at 10 mA/cm². No particular leakcurrent was found even after a lapse of 1000 hours or more.

Incidentally, the results of the practical example 4-7 are also shown inTable 4-2.

Comparative Example 4-1

An organic EL device was fabricated as in the practical example 4-1except that an ITO target was used instead of the target 4-1 of thepractical example 4-1 and an Ag target was used as the metal target.

Incidentally, the work function of the anode layer 412 was 5.25 eV invalue. A direct-current voltage of 5.3 V was applied to across theelectrodes of the obtained organic EL device as in the practical example4-1, with the result that the current density was 2.0 mA/cm in value andthe luminescence intensity was 162 nit. The luminescent color wasconfirmed to be blue.

Incidentally, the results of the comparative example 4-1 are also shownin Table 4-2.

Summary of the Group of Embodiments 4

As has been detailed above, according to the organic EL device which ischaracterized in that an electrode for driving the organicelectroluminescence layer of the present invention comprises an anodethin film layer of a metal oxide having a work function above 5.6 eV anda laminate of metal thin wires, or an electrode substrate for an organicluminescent device, it becomes possible to provide an organic EL devicewhich has excellent transparency and durability and exhibits highluminescent intensity even under a low driving voltage, comprising theanode layer and the like made of certain inorganic compounds.

It was also confirmed that the anode layer and the like made of certaininorganic compounds had excellent etching properties.

Moreover, according to the electrode substrate of the present invention,it is possible to fabricate an organic electroluminescence apparatuswhich provides the foregoing effects.

Moreover, according to the fabrication method of the present invention,it is possible to fabricate an organic electroluminescence apparatuswhich provides the foregoing effects.

Group of Embodiments 5

Hereinafter, a group of preferred embodiments 5 of the present inventionwill be described with reference to the drawings.

Practical Example 5-1 (1) Preparation for the Fabrication of a Substratefor an Organic EL Device (Fabrication of Targets)

Powders of indium oxide and tin oxide (no greater than 1 μm in averageparticle diameter) were accommodated in a wet ball mill container sothat the mole ratio Sn/(In+Sn) was 0.1, followed by mixing and grindingfor 72 hours. Then, the ground article obtained by the foregoing meanswas granulated, and press molded to dimensions of 4 inches in diameterand 5 mm in thickness. The resultant was accommodated in a bakingfurnace, and then heated and baked at a temperature of 1500° C. for 36hours to fabricate a target for the anode layer. This target will bereferred to as an ITO target.

Powders of indium oxide and zinc oxide (no greater than 1 μm in averageparticle diameter) were accommodated in a wet ball mill container sothat the mole ratio Zn/(In+Zn) was 0.15, followed by mixing and grindingfor 72 hours. Then, the ground article obtained by the foregoing meanswas granulated, and press molded to dimensions of 4 inches in diameterand 5 mm in thickness. The resultant was accommodated in a bakingfurnace, and then heated and baked at a temperature of 1400° C. for 36hours to fabricate a target for the anode layer. This target will bereferred to as an IZO target.

Powders of indium oxide and cerium oxide (no greater than 1 μm inaverage particle diameter) were accommodated in a wet ball millcontainer so that the mole ratio Ce/(In+Ce) was 0.18, followed by mixingand grinding for 72 hours. Then, the ground article obtained by theforegoing means was granulated, and press molded to dimensions of 4inches in diameter and 5 mm in thickness. The resultant was accommodatedin a baking furnace, and then heated and baked at a temperature of 1400°C. for 36 hours to fabricate a target for the anode layer. This targetwill be referred to as target 5-1.

Next, a metal target of Ag with additional Cu of 0.7 wt % and Au of 0.8wt % was fabricated. This target will be referred to as an ACA target.

Besides, a metal target of Ag with additional Pd of 0.5 wt % and Cu of1.0 wt % was fabricated. This target will be referred to as an APCtarget.

Besides, a metal target of Al with additional Pt of 0.5 wt % wasfabricated. This target will be referred to as an Al target.

(2) Fabrication of the Substrate for an Organic EL Device

Next, description will be given of the formation of the substrate for anorganic EL device. This is shown in FIG. 15.

A transparent glass substrate of 1.1 mm in thickness, 25 mm in width,and 75 mm in length, as well as the obtained ITO target for the anodelayer, target 5-1 for the anode layer, and Al target, which is a metaltarget, are placed in the vacuum chamber of the high frequencysputtering system. The high frequency sputtering system is operated todepressurize down to an ultimate vacuum of 5×10⁻⁴ Pa, in which state amixed gas of argon gas and 4% oxygen gas is filled. FIG. 15(1) shows theglass substrate, which corresponds to an example of the “base member” inclaims. Incidentally, the base member on which an electrode(s) is/arearranged will be referred to as “electrode substrate.”

In that atmosphere, sputtering was performed by using the ITO targetunder the condition of: a vacuum of 3×10⁻¹ Pa; a substrate temperatureat room temperatures; an input voltage of 100 W; and a film forming timeof 14 minutes. This forms a 110-nm-thick ITO film in the argon gas. Thisis shown in FIG. 15(2).

Then, the Al target was used to form a 120-nm-thick Al thin film in theargon gas. Incidentally, the substrate temperature is 100° C. This isshown in FIG. 15(3).

Subsequently, in a nitrate-phosphate-acetate aqueous solution, the Althin film was etched to form Al thin wires of 20 μm in width. This isshown in FIG. 15(4). These Al thin wires correspond to an example of the“thin wire of metal as auxiliary wire” in claims.

Thereafter, the ITO film of this substrate formed from the ITO targetwas etched in an oxalic aqueous solution so that at least one Al thinwire falls on the side of an ITO electrode made from the ITO target.This is shown in FIG. 15(5). The electrode fabricated through suchpatterning will be referred to as a patterning electrode.

Incidentally, the ITO film formed from the ITO target preferably has awidth of 90 μm.

Next, this substrate and a substrate having no film were put back intothe vacuum chamber, and a 20-nm thin film of a metal oxide was formed byusing the target 5-1 at a substrate temperature of 200° C. over theentire surface excluding an electrode outlet. This is shown in FIG.15(6). This substrate for an organic EL device corresponds to an exampleof the electrode substrate for an organic electroluminescence device inclaims.

Next, this substrate was subjected to ultrasonic cleaning in isopropylalcohol, and then dried in a N₂ (nitrogen gas) atmosphere before10-minute cleaning by using UV (ultraviolet rays) and ozone.

(3) Measurements

After the UV cleaning of the substrate, the anode layer was measured forthe value of its work function by using AC-1 (from Riken Keiki Co.,Ltd.), and found to be 6.18 eV (after cleaning). Moreover, the substrateprovided with the anode layer was measured for light transmittance(wavelength of 550 nm) and found to be 88%. The patterning electrode(electrode width: 90 μm, electrode length: 100 mm) described above wasmeasured for resistance by the two probe method, and found to be 2.5 kΩ.The thin film layer of the metal oxide formed from the target 5-1 alonewas 5×10 E+5 Ωcm in specific resistance.

Incidentally, the measurements are shown in Table 5-1.

(4) Formation of the Organic EL Device

The foregoing “substrate” was loaded on the substrate holder in thevacuum chamber of the vacuum evaporator. Then, the vacuum chamber wasdepressurized inside to a vacuum of 1×10⁻⁶ Torr or lower before a holetransporting layer 520, an organic luminescent layer 522, an electroninjection layer 524, and a cathode layer 526 were laminated insuccession on the anode layer of the substrate to obtain an organic ELdevice 530. This is shown in FIG. 18.

Here, in the period from the formation of the organic luminescent layerto the formation of the cathode layer, the vacuum was not broken evenonce so that the same vacuum condition was maintained.

Here, the organic EL device corresponds to the organic EL light emittingapparatus in claims.

Initially, as the hole transporting material, TBDB was vacuum-evaporatedto 60 nm. Next, as the luminescent layer, DPVDPAN and D1 wereco-evaporated to 40 nm in the vacuum. Here, the deposition rate of theDPVDPAN was 40 nm/s and the deposition rate of D1 was 1 nm/s.

Then, as the electron injection layer, Alq was vacuum-evaporated to 20nm. Finally, Al and Li were vacuum-evaporated to form the cathode layeron the electron injection layer, fabricating the organic EL device.

Here, the deposition rate of Al was 1 nm/s, and the deposition rate ofLi was 0.01 nm/s. The thickness of the Al/Li film was 200 nm.

Incidentally, these are shown in Table 5-1. Moreover, the chemicalformulae of TBDB, DPVDPAN, D1, and Alq are shown in FIG. 19.

(5) Evaluation on the Organic EL Device

A direct-current voltage of 4.3 V was applied to across electrodes withthe cathode layer of the obtained organic EL device as the negative (−)electrode and the anode layer as the positive (+) electrode.

Here, the current density was 2.0 mA/cm² and the luminescence intensitywas 163 nit (cd/m²). The luminescent color was confirmed to be blue.Furthermore, for the sake of durability evaluation, constant-currentdriving was conducted at 10 mA/cm². No particular leak current was foundeven after a lapse of 1000 hours or more.

Incidentally, the results of the practical example 5-1 are shown inTable 5-1.

TABLE 5-1 Practical Practical Practical Practical embodiment embodimentembodiment embodiment 5-1 5-2 5-3 5-4 Material of anode layer ITO + AlITO + Al IZO + Al ITO + APC (Auxiliary wiring) Protective layer of metaloxide In oxide/ In oxide/ In oxide/ In oxide/ Ce oxide Sn oxide/ Znoxide/ Zn oxide/ Ce oxide Ce oxide Sm oxide Work function (eV) (aftercleaning) 6.18 6.05 5.95 5.90 Light transmittance (%) * 88 88 89 88Electrode resistance (kΩ) 2.5 2.4 2.6 2.3 Specific resistance of metaloxide thin 10E+5 10E+5 10E+7 10E+6 film layer (Ω cm) Hole transportingmaterial TBDB TBDB TBDB TBDB Thickness (nm) 60 60 60 60 Material ofluminescent layer DPVDPAN DPVDPAN DPVDPAN DPVDPAN Thickness (nm) 40 4040 40 Material electron injection layer Alq Alq Alq Alq Thickness (nm)20 20 20 20 Material of cathode layer Al/Li Al/Li Al/Li Al/Li Thickness(nm) 200 200 200 200 Voltage (V) 4.3 4.2 4.6 4.4 Luminescence intensity(cd/m²) 163 158 163 158 Half life 1000 hours 1000 hours 1000 hours 1000hours or more or more or more or more * Glass reference

While the glass substrate was used in the present practical example 5-1,the “base member” may also be a glass substrate, a plastic substrate, asilicon wafer, a color-filtered color conversion substrate, or the like.

Practical Example 5-1 #2

For a modified example of the practical example 5-1, the order oflamination may be inverted of the transparent conductive thin filmcomposed mainly of indium oxide and the metal thin film as an auxiliarywire. Even in such configuration, the functions and effects of theinvention are the same as in the foregoing practical example 5-1.Incidentally, FIG. 17 shows a sectional view of the configuration wherethe order of lamination is inverted.

Practical Example 5-2

A target 5-2 shown below was used instead of the target 5-1 of thepractical example 5-1. The organic EL device was fabricated in the samemanner as in the practical example 5-1 except that the target 5-2 wasused.

The target 5-2 is composed of indium oxide, tin oxide, and cerium oxide.The mole ratio of indium (In/(In+Sn)) is 0.9, the mole ratio of tin(Sn/(In+Sn)) is 0.1, and the mole ratio of cerium to the total metal(Ce/(In+Sn+Ce)) is 0.16.

Incidentally, the work function of the anode layer was 6.05 eV in value.The electrode resistance was 2.4 kΩ. A direct-current voltage of 4.2 Vwas applied to across the electrodes of the obtained organic EL deviceas in the practical example 5-1, with the result that the currentdensity was 2.0 mA/cm² in value and the luminescence intensity was 158nit. The luminescent color was confirmed to be blue. Furthermore, forthe sake of durability evaluation, constant-current driving wasconducted at 10 mA/cm². No particular leak current was found even aftera lapse of 1000 hours or more.

Incidentally, the results of the practical example 5-2 are also shown inTable 5-1.

Practical Example 5-3

A target 5-3 shown below was used instead of the target 5-1 of thepractical example 5-1. The organic EL device was fabricated in the samemanner as in the practical example 5-1 except that the target 5-3 wasused.

The target 5-3 is composed of indium oxide, zinc oxide, and ceriumoxide. The mole ratio of indium (In/(In+Zn)) is 0.9, the mole ratio ofzinc (Zn/(In+Zn)) is 0.1, and the mole ratio of cerium to the totalmetal (Ce/(In+Zn+Ce)) is 0.15.

Incidentally, the work function of the anode layer was 5.95 eV in value.The electrode resistance was 2.6 kΩ. A direct-current voltage of 4.6 Vwas applied to across the electrodes of the obtained organic EL deviceas in the practical example 5-1, with the result that the currentdensity was 2.0 mA/cm² in value and the luminescence intensity was 163nit. The luminescent color was confirmed to be blue. Furthermore, forthe sake of durability evaluation, constant-current driving wasconducted at 10 mA/cm². No particular leak current was found even aftera lapse of 1000 hours or more.

Incidentally, the results of the practical example 5-3 are also shown inTable 5-1.

Practical Example 5-4

A target 5-4 shown below was used instead of the target 5-1 of thepractical example 5-1. As for the metal target, the APC target was usedinstead of the Al target. In other respects, the organic EL device wasfabricated in the same manner as in the practical example 5-1.

The target 5-4 is composed of indium oxide, tin oxide, and samariumoxide. The mole ratio of indium (In/(In+Zn)) is 0.9, the mole ratio oftin (Sn/(In+Sn)) is 0.1, and the mole ratio of samarium to the totalmetal (Sm/(In+Zn+Sm)) is 0.18.

Incidentally, the work function of the anode layer was 5.90 eV in value.The electrode resistance was 2.3 kΩ. A direct-current voltage of 4.4 Vwas applied to across the electrodes of the obtained organic EL deviceas in the practical example 5-1, with the result that the currentdensity was 2.0 mA/cm² in value and the luminescence intensity was 158nit. The luminescent color was confirmed to be blue. Furthermore, forthe sake of durability evaluation, constant-current driving wasconducted at 10 mA/cm². No particular leak current was found even aftera lapse of 1000 hours or more.

Incidentally, the results of the practical example 5-4 are also shown inTable 5-1.

TABLE 5-2 Practical Practical Practical Comparative embodimentembodiment embodiment example 5-5 5-6 5-7 5-1 Material of anode layerIZO + ACA IZO + APC ITO + ACA IZO + Al (Auxiliary wiring) Protectivelayer of metal oxide In oxide/ In oxide/ In oxide/ In oxide/ Sn oxide/Sn oxide/ Sn oxide/ Sn oxide/ Pr oxide Nd oxide/ Tb oxide Work-function(eV) 5.84 5.82 5.95 5.25 (after cleaning) Light transmittance (%) * 8888 87 89 Electrode resistance (kΩ) 2.6 2.7 2.6 2.6 Specific resistanceof metal oxide 10E+6 10E+6 10E+7 10E−4 thin film layer (Ω cm) Holetransporting TBDB TBDB TBDB TBDB material Thickness (nm) 60 60 60 60Material of luminescent layer DPVDPAN DPVDPAN/ DPVDPAN/ DPVDPAN/ D1 D1D1 D1 Thickness (nm) 40 40 40 40 Material electron injection layer AlqAlq Alq Alq Thickness (nm) 20 20 20 20 Material of cathode layer Al/LiAl/Li Al/Li Al/Li Thickness (nm) 200 200 200 200 Voltage (V) 4.5 4.5 4.65.2 Luminescence intensity (cd/m²) 166 165 161 Half life 1000 hours 1000hours 1000 hours or more or more or more * Transmittance: Glassreference

Practical Example 5-5

A target 5-5 shown below was used instead of the target 5-1 of thepractical example 5-1. As for the metal target, the ACA target was usedinstead of the Al target. In other respects, the organic EL device wasfabricated in the same manner as in the practical example 5-1.

The target 5-5 is composed of indium oxide, tin oxide, and praseodymiumoxide. The mole ratio of indium (In/(In+Sn)) is 0.9, the mole ratio oftin (Sn/(In+Sn)) is 0.1, and the mole ratio of praseodymium to the totalmetal (Pr/(In+Sn+Pr)) is 0.20.

Incidentally, the work function of the anode layer was 5.84 eV in value.The electrode resistance was 2.6 kΩ. A direct-current voltage of 4.5 Vwas applied to across the electrodes of the obtained organic EL deviceas in the practical example 5-1, with the result that the currentdensity was 2.0 mA/cm² in value and the luminescence intensity was 166nit. The luminescent color was confirmed to be blue. Furthermore, forthe sake of durability evaluation, constant-current driving wasconducted at 10 mA/cm². No particular leak current was found even aftera lapse of 1000 hours or more.

Incidentally, the results of the practical example 5-5 are shown inTable 5-2.

Practical Example 5-6

A target 5-6 shown below was used instead of the target 5-1 of thepractical example 5-1. As for the metal target, the APC target was usedinstead of the Al target. In other respects, the organic EL device wasfabricated in the same manner as in the practical example 5-1.

The target 5-6 is composed of indium oxide, tin oxide, and neodymiumoxide. The mole ratio of indium (In/(In+Sn)) is 0.9, the mole ratio oftin (Sn/(In+Sn)) is 0.1, and the mole ratio of neodymium to the totalmetal (Nd/(In+Sn+Nd)) is 0.15.

Incidentally, the work function of the anode layer was 5.82 eV in value.The electrode resistance was 2.7 kΩ. A direct-current voltage of 4.5 Vwas applied to across the electrodes of the obtained organic EL deviceas in the practical example 5-1, with the result that the currentdensity was 2.0 mA/cm² in value and the luminescence intensity was 165nit. The luminescent color was confirmed to be blue. Furthermore, forthe sake of durability evaluation, constant-current driving wasconducted at 10 mA/cm². No particular leak current was found even aftera lapse of 1000 hours or more.

Incidentally, the results of the practical example 5-6 are also shown inTable 5-2.

Practical Example 5-7

A target 7 shown below was used instead of the target 5-1 of thepractical example 5-1. As for the metal target, the ACA target was usedinstead of the Al target. In other respects, the organic EL device wasfabricated in the same manner as in the practical example 5-1.

The target 7 is composed of indium oxide, tin oxide, and terbium oxide.The mole ratio of indium (In/(In+Sn)) is 0.9, the mole ratio of tin(Sn/(In+Sn)) is 0.1, and the mole ratio of terbium to the total metal(Tb/(In+Sn+Tb)) is 0.16.

Incidentally, the work function of the anode layer was 5.95 eV in value.The electrode resistance was 2.6 kΩ. A direct-current voltage of 4.6 Vwas applied to across the electrodes of the obtained organic EL deviceas in the practical example 5-1, with the result that the currentdensity was 2.0 mA/cm² in value and the luminescence intensity was 161nit. The luminescent color was confirmed to be blue. Furthermore, forthe sake of durability evaluation, constant-current driving wasconducted at 10 mA/cm². No particular leak current was found even aftera lapse of 1000 hours or more.

Incidentally, the results of the practical example 5-7 are also shown inTable 5-2.

Comparative Example 5-1

An organic EL device was fabricated as in the practical example 5-1except that an IZO target was used instead of the target 5-1 of thepractical example 5-1 and an Al target was used as the metal target.

Incidentally, the work function of the anode layer was 5.25 eV in value.A direct-current voltage of 5.2 V was applied to across the electrodesof the obtained organic EL device as in the practical example 5-1, withthe result that the current density was 2.0 mA/cm² in value. Theluminescent color was confirmed to be blue. Nevertheless, due to acurrent flowing between anode electrodes, single-pixel luminescence wasimpossible which precluded simple matrix driving.

Incidentally, the results of the comparative example 5-1 are also shownin Table 5-2.

Summary of the Group of Embodiments 5

As has been detailed above, by using the electrode substrate for anorganic electroluminescence device of the present invention toconstitute an organic EL light emitting apparatus, it has becomepossible to provide an organic EL light emitting apparatus which hasexcellent transparency and durability and exhibits high luminescenceintensity even under a low driving voltage, comprising the anode layerand the like made of certain inorganic compounds. It was also confirmedthat the anode layer and the like made of certain inorganic compoundshad excellent etching properties.

Besides, according to the organic EL device of the present invention, ithas become possible to provide an organic EL device effectively whichhas excellent transparency and durability and exhibits high luminescenceintensity even under a low driving voltage.

1. A sputtering target comprising: a sintered article; and a backingplate comprising a metal bonded to the sintered article, wherein thesintered article comprises: at least one metal oxide selected from thegroup consisting of indium oxide, zinc oxide, and tin oxide, wherein themetal component of the metal oxide is present in an amount of at least80 atomic %, based on a total amount of metal present in the sinteredarticle; and at least one additional metal oxide selected from the groupconsisting of hafnium oxide, tantalum oxide, bismuth oxide, and alanthanide metal oxide, wherein the metal component of the additionalmetal oxide is present in an amount of 1-20 atomic %, based on a totalamount of metal present in the sintered article.
 2. The sputteringtarget according to claim 1, wherein the metal component of the metaloxide is present in an amount of 80-99 atomic %, based on a total amountof metal present in the sintered article.
 3. The sputtering targetaccording to claim 1, wherein the sintered article is in a form of aflatly-worked piece of sintered article.
 4. The sputtering targetaccording to claim 1, wherein the metal oxide is indium oxide.
 5. Thesputtering target according to claim 1, wherein the metal oxide is zincoxide.
 6. The sputtering target according to claim 1, wherein the metaloxide is tin oxide.
 7. The sputtering target according to claim 1,wherein the metal oxide is indium oxide and zinc oxide.
 8. Thesputtering target according to claim 1, wherein the metal oxide isindium oxide and tin oxide.
 9. The sputtering target according to claim1, wherein the metal oxide is zinc oxide and tin oxide.
 10. Thesputtering target according to claim 1, wherein the metal oxide isindium oxide, zinc oxide, and tin oxide.
 11. The sputtering targetaccording to claim 1, wherein the additional metal oxide is hafniumoxide.
 12. The sputtering target according to claim 1, wherein theadditional metal oxide is tantalum oxide.
 13. The sputtering targetaccording to claim 1, wherein the additional metal oxide is bismuthoxide.
 14. The sputtering target according to claim 1, wherein theadditional metal oxide is a lanthanide metal oxide.
 15. The sputteringtarget according to claim 14, wherein the additional metal oxide is alanthanide metal oxide selected from the group consisting of ceriumoxide, samarium oxide, europium oxide, terbium oxide, and combinationsthereof.
 16. The sputtering target according to claim 15, wherein theadditional metal oxide is cerium oxide.
 17. The sputtering targetaccording to claim 15, wherein the additional metal oxide is samariumoxide.
 18. The sputtering target according to claim 15, wherein theadditional metal oxide is europium oxide.
 19. The sputtering targetaccording to claim 15, wherein the additional metal oxide is terbiumoxide.
 20. The sputtering target according to claim 15, wherein theadditional metal oxide is cerium oxide, samarium oxide, europium oxide,and terbium oxide.
 21. The sputtering target according to claim 1,wherein the additional metal oxide is hafnium oxide, tantalum oxide,bismuth oxide, and a lanthanide metal oxide.
 22. The sputtering targetaccording to claim 21, wherein the additional metal oxide is alanthanide metal oxide selected from the group consisting of ceriumoxide, samarium oxide, europium oxide, terbium oxide, and combinationsthereof.
 23. The sputtering target according to claim 22, wherein theadditional metal oxide is cerium oxide.
 24. The sputtering targetaccording to claim 22, wherein the additional metal oxide is samariumoxide.
 25. The sputtering target according to claim 22, wherein theadditional metal oxide is europium oxide.
 26. The sputtering targetaccording to claim 22, wherein the additional metal oxide is terbiumoxide.
 27. The sputtering target according to claim 22, wherein theadditional metal oxide is cerium oxide, samarium oxide, europium oxide,and terbium oxide.
 28. The sputtering target according to claim 1, whichhas a transparency of at least 87%.
 29. The sputtering target accordingto claim 1, which has a transparency of at least 88%.
 30. The sputteringtarget according to claim 1, which has a transparency of at least 89%.31. The sputtering target according to claim 1, which has a workfunction of at least 5.50 eV.
 32. The sputtering target according toclaim 1, which has a work function of at least 5.60 eV.
 33. Thesputtering target according to claim 1, which has a work function of atleast 5.70 eV.